Bartonella and Brain Fog
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Quick answer
Evidence
Bartonella can affect the nervous system and cause problems with thinking.
Evidence consensus
High for acute infection; Controversial for chronic symptom attribution
CDC Bartonella guidelines; recognized infection criteria
Evidence and recovery context
Evidence
Bartonella can affect the nervous system and cause problems with thinking.
Key distinction
Brain fog alone is weak evidence. Physical and neurological clues matter.
- of domestic and shelter cats in some populations had B. henselae in their blood
- 30-40%
- people in a 2026 Bartonella encephalitis cohort reported cognitive problems at long-term follow-up
- 8/19
- investigating, diagnosed and supporting someone
- 3paths
Investigating: I think it might be Bartonella
Can Bartonella cause brain fog?
Yes, when the infection affects the nervous system.
The clearest human evidence comes from neurological disease. In a 2026 study of cat-scratch disease encephalitis, 8 of 19 people reported cognitive problems at long-term follow-up. Reports of nervous-system Bartonella also describe memory loss, confusion and cognitive decline. (1) (2)
Bartonella is likelier when thinking changes appear with harder-to-explain signs, such as burning nerve pain, neuroretinitis (optic nerve swelling), unusual skin lesions, swollen glands after cat exposure, or major neurological or behavioural changes.
What does Bartonella brain fog feel like?
Bartonella-related cognitive problems can include poor concentration, memory trouble, slowed thinking and difficulty processing what is happening around you.
Published neurological cases describe memory loss, disorientation and cognitive decline. WBF community research also found people describing brain fog as one part of a larger illness, often with agitation, poor sleep, nerve pain or other physical symptoms. (2)
The mix of symptoms matters more than how you describe the brain fog. Poor concentration alone has many common causes. If thinking changes start with burning feet, vision problems, unusual skin changes or symptoms when you stand up, each of those needs checking too. Tell your doctor about all of them at once.
How could Bartonella cause brain fog?
Bartonella probably affects thinking in several ways. The infection can affect nerves, blood vessels and inflammation. Pain, poor sleep and dysautonomia can also cause problems with thinking.
Bartonella can affect both the central and peripheral nervous systems. B. henselae can also enter endothelial cells, the cells that line blood vessels, and may alter inflammatory and blood-vessel growth pathways. (2) (3)
This connects findings that otherwise look unrelated. Skin lesions, eye disease, nerve pain and thinking problems can come from one illness that affects nerves and blood vessels.
What is VEGF?
VEGF stands for vascular endothelial growth factor. It helps control how new blood vessels grow. Inside infected tissue, Bartonella can change how that growth is controlled.
What symptoms make Bartonella worth investigating?
Bartonella becomes worth investigating when brain fog is joined by a compatible exposure and a physical or neurological clue that is harder to explain.
Stronger findings
- tender regional lymph nodes after cat or kitten exposure
- a bump or pustule where a scratch or bite occurred
- burning, shooting or unusually sensitive foot pain
- blurred or reduced vision from neuroretinitis
- unusual red, purple or striae-like skin lesions
Wider-system findings
- sudden neurological or behavioural change
- fever with liver or spleen involvement
- culture-negative endocarditis
- marked orthostatic symptoms or dysautonomia
- a plausible cat, flea or body-louse exposure
Counting symptoms cannot give you a real probability of Bartonella. Ask whether the exposure, timing, organ findings and test choice all make sense together.
Exposure Screener
History Builder
Bartonella exposure and findings checklist
This checklist helps you list what you've been exposed to and which body parts are affected, ready to discuss with a clinician.
What can you do now?
You do not need to wait for a Bartonella test before acting on the parts of the problem that are already clear.
Prevent new exposure
If you live with cats, keep flea prevention current and reduce scratches and bites. Clean fresh scratches or bites with soap and water. Keep cats from licking broken skin. For B. quintana, body-lice control matters. CDC guidance
Get eye symptoms checked now
New blurred vision, a blind spot or sudden loss of vision changes the priority. Neuroretinitis can keep developing after symptoms begin, so get an eye assessment now, before the rest of the Bartonella work-up. (9)
Check whether standing makes thinking worse
If your thinking is much worse standing up and better lying down, get that checked now. POTS can cause brain fog on its own. Open the POTS guide
Choose the test that fits the finding
A swollen lymph node, neuroretinitis, bacteremia and endocarditis each need different tests.
Symptoms and body systems
Can Bartonella cause rage, anxiety or psychiatric symptoms?
Reports link Bartonella to sudden psychiatric and behavioural symptoms, but rage or anxiety alone does not point to Bartonella.
Published neurobartonellosis reports include panic, agitation, personality change and psychosis. A 2024 blinded study detected Bartonella DNA more often in adults with psychosis than in controls. This link does not show Bartonella explains psychiatric illness in general. (2) (4)
If you've had bursts of rage or irritability that feel unlike you, go easy on yourself and skip the guilt. Neurological illness can affect mood and behaviour. Bartonella is one possible cause of rage or anxiety when nerve pain, cognitive change, skin lesions or other neurological or physical signs appear alongside the change. The behaviour still matters, but it doesn't have to define you.
Can Bartonella cause insomnia or broken sleep?
Reports describe poor sleep in Bartonella illness, but there's no good evidence that waking at a set clock time is a sign of Bartonella.
Insomnia appears in neurological and psychiatric Bartonella reports. Pain can wake someone. Autonomic symptoms can cause palpitations or sweating. Agitation can make it hard to settle. Poor sleep then becomes its own cause of brain fog the next day. (2)
Can Bartonella cause burning feet or foot pain?
Published reports describe burning feet, sole pain, tingling and other forms of nerve pain in Bartonella infections.
One PCR-confirmed case progressed from ankle pain to swelling, colour changes and heightened pain sensitivity in both feet. Other reports describe painful toe lesions with polyneuropathy and pain in the bottoms of the feet. (2) (5) (6) Complex regional pain syndrome case with B. koehlerae
Burning, shooting pain, extreme sensitivity, colour change or other neuropathic features are more informative than ordinary aching feet.
What do Bartonella skin lesions look like?
There is no single Bartonella rash.
Classic cat-scratch disease can start with a red bump, pustule or blister where the bacteria entered the skin. Other Bartonella disease can involve vascular or inflammatory skin lesions.
The red or purple lines that resemble stretch marks are a newer part of the literature. In one 29-person study, 24 people reported some form of skin lesion, but only 14 had linear lesions. The often-repeated 83% figure does not mean 83% had Bartonella streaks. (7)
One striae-like skin biopsy also contained B. henselae DNA. A skin mark matters more when it is part of a neurological or systemic illness. (8)
Can Bartonella affect your eyes or vision?
Bartonella can cause neuroretinitis, inflammation of the optic nerve and nearby retina that can produce sudden blurred or reduced vision.
B. henselae is a recognised infectious cause of neuroretinitis. People may notice a central blind spot, reduced sharpness or altered colour vision. The classic star shape in the retina may appear after vision symptoms begin. (9) Neuroretinitis review, 2018
A 2024 case had negative Bartonella serology at first; repeat testing later supported the diagnosis as the retinal findings evolved. Eye changes and a positive blood test can both appear later. (10)
Sudden loss of vision or a new blind spot needs urgent eye assessment.
Can Bartonella cause swollen lymph nodes?
A large, tender lymph node near the site of a scratch or bite is one of the strongest classic signs of cat-scratch disease.
The nodes drain the area where the bacteria entered, so common sites include the armpit, neck and groin. WBF community research repeatedly found people remembering a striking lump in the neck, face or armpit after cat exposure. Some first got a diagnosis of mono, mumps or another illness. (11)
Can you have Bartonella without swollen glands or fever?
You can have Bartonella without the classic fever-and-swollen-node presentation.
Bartonella can affect the eyes, nervous system, liver, spleen, bones or heart. Without fever or swollen glands, classic cat-scratch disease is less obvious, but other Bartonella forms are still possible. Atypical cat-scratch disease study, United States, 2020
Can Bartonella trigger POTS or dysautonomia?
Like some other infections, Bartonella may trigger or uncover dysautonomia, but research has not shown a direct path to POTS.
POTS can involve autonomic neuropathy, low effective blood volume, immune mechanisms, vascular control and sympathetic overactivity. Infection is a recognised trigger for some people. Bartonella can affect peripheral nerves and endothelial cells, giving it several possible routes to worsen autonomic control without requiring one simple POTS mechanism. (12) (2) Bartonella autonomic function study, 2026
If brain fog gets sharply worse upright and improves lying down, investigate the orthostatic problem separately. POTS is not proof of Bartonella.
Can Bartonella affect the heart, liver or spleen?
Bartonella can involve the heart, liver and spleen. These complications show why Bartonella is not one disease with one test or treatment course.
Can Bartonella cause endocarditis?
Bartonella species are important causes of blood-culture-negative endocarditis. Routine blood cultures can stay negative even when Bartonella infects a heart valve. Valve-tissue PCR can be much more informative than blood PCR in that setting. (13)
Can Bartonella affect the liver or spleen?
Hepatosplenic cat-scratch disease can cause prolonged fever, fatigue, abdominal pain, enlarged liver or spleen and small lesions seen on imaging. Published reports describe it in children and adults. (14)
Can you get Bartonella without a cat scratch?
Bartonella is still possible even if you cannot remember a cat scratch.
For B. henselae, fleas are central to the usual transmission chain. Flea faeces can contaminate a cat's claws, and a scratch can push the bacteria through the skin. Cats can look healthy while carrying B. henselae. Cat bites and an infected cat licking an open wound are also recognised routes. (15)
What about ticks?
Research hasn't shown people catch Bartonella from tick bites, and current CDC guidance doesn't list ticks as a proven source. Researchers have found Bartonella DNA in ticks, and experiments haven't settled the question.
What about body lice?
Body-louse faeces spread B. quintana, which can cause repeated fevers, long-lasting blood infection and endocarditis.
What about rodents?
Rodents carry several Bartonella species, and published reports describe human infections with rodent-associated species. That is different from assuming any rat exposure caused B. henselae.
Should you test a healthy cat?
Testing a healthy cat does not tell you whether your symptoms are Bartonella. CDC veterinary guidance does not recommend testing or treating a healthy cat just to assess an owner's risk. Flea prevention matters more.
Does Bartonella look different in children and adults?
Classic cat-scratch disease is more common in children, but adults can develop classic and atypical Bartonella disease.
Cat-scratch disease disproportionately affects people under 15. Lymph-node swelling dominates many paediatric presentations, although eye, bone, liver, spleen and neurological disease also occur. Adults can present with lymphadenopathy too, while adult literature also includes neuroretinitis, hepatosplenic disease, bacteremia and endocarditis. (16)
Can Bartonella tests be negative even if you have it?
A negative Bartonella result can mean different things depending on the test, the sample and the timing.
Finding Bartonella depends on the sample as well as the test. One negative blood test can look conclusive when bacteria are scarce in blood or concentrated somewhere else.
In a 25-year cat-scratch disease study, PCR detected Bartonella in 96% of lymph-node pus samples but 59% of paraffin-embedded lymph-node tissue. In a high-risk cohort, 30.4% of bacteremic participants had no IFA antibodies. Direct blood PCR alone would have missed 16 of the 46 infections eventually detected using combined testing. (17) (18)
Timing can matter too. In another study, testing three blood collections during one week detected Bartonella in 33.3% of participants compared with 12.7% using one collection. (19)
| Test | What it can tell you |
|---|---|
| IFA / serology | Looks for antibodies. Results vary between assays, cross-reactions occur and antibodies can remain after infection. |
| Blood PCR | Looks for Bartonella DNA directly. One draw can miss low or intermittent bacteremia. |
| Enrichment + PCR | Gives small amounts of Bartonella time to multiply before PCR. Human studies have found infections missed by direct PCR. |
| Lymph-node / lesion PCR | Can be much more informative when bacteria are concentrated in the affected site. |
| Heart-valve PCR | Can be especially useful in suspected culture-negative Bartonella endocarditis when valve tissue is available. |
| Repeat samples | Can catch infections that a single blood draw misses. |
| mNGS | Broad sequencing increasingly reported in difficult or atypical cases. |
Why can serology and PCR disagree?
They answer different questions. Serology asks whether the immune system has made antibodies. PCR asks whether bacterial DNA is present in the sample.
What about enrichment PCR?
Much of the human evidence for BAPGM, an enrichment method, comes from the research group that helped develop it, so no one should call it a universal gold standard. (20) Duncan AW, Maggi RG, Breitschwerdt EB. J Microbiol Methods. 2007
A better testing question
What form of Bartonella disease are we looking for, and which sample has the best chance of answering that question?
Is Bartonella the same as Lyme disease?
Bartonella and Lyme disease are different infections, although they can occur in the same person.
Fatigue, brain fog, poor sleep and pain happen in both. Problems in particular organs tell them apart better.
| Possibility | Findings that deserve weight |
|---|---|
| Bartonella | Cat/flea or body-louse exposure depending on species, regional lymph nodes, neuroretinitis, culture-negative endocarditis, neuropathic foot pain and some unusual skin lesions. |
| Lyme disease | Tick exposure, erythema migrans, facial palsy, meningitis or radicular pain, or a swollen large joint such as a knee. |
| Babesia | Tick exposure with fever, chills or sweats, haemolytic anaemia, low platelets, jaundice or dark urine. |
| POTS / dysautonomia | Symptoms clearly start or worsen when upright, with heart-rate rise, dizziness, weakness or worse thinking. |
| Anxiety / depression | They can cause poor sleep and concentration, but on their own they don't explain neuroretinitis, endocarditis or Bartonella DNA in an appropriate sample. |
| MCAS | Flushing, hives, itching and reactions that keep coming back can suggest mast-cell disease. |
Can you have Bartonella, Lyme disease or Babesia at the same time?
Human studies have found Bartonella alongside both Babesia and Lyme bacteria (Borrelia).
In a 2024 molecular case series, 6 of 7 people with confirmed Babesia odocoilei also had one or more Bartonella species. A 2026 study of 50 people with long-term fatigue and neurological symptoms found Babesia in 12, Bartonella in 13, and both in 2. Earlier neurological research also documented mixed B. henselae and B. burgdorferi infections. (21) (22) (23)
These rates describe selected patient groups only. Having both doesn't show that a tick passed on the Bartonella.
Can Bartonella be chronic or come back?
Bartonella can persist or recur in some settings, but the phrase "chronic Bartonella" is too vague to describe one single medical problem.
"Chronic Bartonella" can mean persistent bacteremia, an infection in a particular organ, recurrent cat-scratch disease, or symptoms that continue after the infection settles.
Persistent bacteremia
Studies confirm B. quintana can stay in the blood, and a randomized trial tested treating it.
Persistent organ infection
Endocarditis and other disseminated infections are different problems from ordinary cat-scratch lymphadenitis.
Recurrence
Published reports describe recurrent cat-scratch disease, but it appears uncommon. Recurrence and reinfection can be difficult to separate.
Lingering recovery
Brain fog or nerve symptoms can outlast the obvious acute illness without proving bacteria remain active.
A childhood history is worth mentioning, but current evidence does not justify assuming every childhood infection remains active for decades.
How is Bartonella treated?
Treatment depends on which Bartonella disease a person actually has. There is no useful universal Bartonella treatment course.
A swollen lymph node after cat-scratch disease, neuroretinitis and Bartonella endocarditis are all Bartonella, but they are not the same treatment problem.
Typical cat-scratch disease in an otherwise healthy person often settles without prolonged antibiotic treatment. The approach changes when Bartonella involves the eye, nervous system, bloodstream or heart valve. (16)
That's why a fixed claim like "Bartonella needs four to six months of antibiotics" is misleading. The short course used for swollen glands in simple cat-scratch disease won't fit every complicated infection either.
Why can Bartonella be hard to treat?
Bartonella can live in different biological environments, and those environments do not respond identically to antibiotics.
Bartonella can grow outside cells, inside host cells and in biofilms. A 2026 laboratory study found that single antibiotics could suppress extracellular B. henselae yet failed to eliminate established intracellular infection or biofilms in those experimental models. Some combinations reduced bacterial survival more effectively. (24)
There is human evidence for combination treatment in specific disease forms too. In a randomized trial of chronic B. quintana bacteremia, bacteremia cleared in 7 of 9 treated participants compared with 2 of 11 untreated controls. (25)
Persistence inside cells or biofilms can make Bartonella hard to clear, even without antibiotic resistance.
Can Bartonella treatment make you feel worse at first?
A Jarisch-Herxheimer-type reaction can occur with Bartonella treatment, but some symptom flares during treatment have other causes.
Published reports describe Jarisch-Herxheimer-type reactions with cat-scratch disease and B. quintana. Those reactions come on quickly. Weeks of worsening brain fog don't prove that bacteria are dying. (26) (27)
Side effects, drug interactions, allergic reactions, a progressing illness or another condition can also make you feel worse.
A treatment flare is not proof that Bartonella was the right diagnosis, and it is not proof that treatment is working.
What supplements have actual Bartonella research?
Some supplements used around Bartonella have direct laboratory evidence. Others have Bartonella-specific host-cell evidence or indirect evidence. Those are different claims.
Direct anti-Bartonella laboratory evidence
Cryptolepis
Cryptolepis killed stationary-phase B. henselae in a seven-day culture experiment.
Japanese knotweed
Many Bartonella herbal protocols use Japanese knotweed. It was active against both growing and non-growing B. henselae.
Chinese skullcap
Chinese skullcap showed anti-Bartonella activity, but was weaker than Japanese knotweed and Cryptolepis in the longer kill experiment. Reports describe rare liver injury.
Source: Botanical study
Bartonella-specific host-cell evidence
L-arginine
Bartonella can infect cells that help repair blood vessels. In a lab-dish study of human cells, L-arginine reduced the damage. It has never been tested in people with Bartonella. (3)
Indirect support
NAC
Bartonella can form biofilms. NAC can disrupt bacterial biofilms.
Curcumin
Bartonella activates NF-kB inflammatory signalling. Curcumin can suppress that pathway.
What people remember about Bartonella
WBF community research kept finding three themes. People had a large lymph node in one area after cat exposure. First diagnoses included mono, mumps, migraine and stress. Brain fog was one part of a larger, strange illness.
- My story with possible bartonella
A 16-year-old describes a history of depression, fatigue and swollen abdominal lymph nodes. They say doctors misread recent delusions, psychosis and mania as schizophrenia or bipolar disorder. A functional psychiatrist now suspects chronic Bartonella, citing signs like purple streaks on the back that resemble stretch marks.
- My symptoms\Story of Bartonella
The poster's illness began in childhood with depression, anxiety, OCD-like rumination, bursts of anger and fatigue so severe they could not stay awake in school. Their thinking got steadily worse. By late high school they napped every day just to survive normal life.
- Please Is There Cure for Bartonella Brainfog?
The poster says fatigue improved, but they still don't feel fully present, even while functioning. Replies suggest Burbur and Pinella for inflammation in the head, a Denneroll neck support for alignment and blood flow, and methylene blue as one of the few things that made a huge difference.
Doctor Prep
What should I ask my doctor about Bartonella?
Bring the combination of exposure, symptoms and organ-specific findings. Lead with that, not a demand for one commercial test.
"I have brain fog plus [nerve pain / skin changes / vision symptoms / swollen glands / other symptoms] and a history of [cat / kitten / flea / body-louse exposure]. Could Bartonella explain this? If testing makes sense, which test and which sample fit the kind of illness you're considering?"
What would weaken the Bartonella case?
- brain fog occurs alone, with no compatible exposure or physical findings
- a common condition explains the symptoms well
- repeat testing suited to the suspected disease form stays negative
- the case depends entirely on a long generic symptom list
- the only supporting argument is feeling worse during treatment
Which Bartonella symptoms need faster assessment?
Some Bartonella complications involve the brain, eyes, heart, liver or spleen. These need faster medical assessment than routine brain fog.
- sudden loss of vision, a new blind spot or major visual change
- seizure, severe confusion, fainting, new weakness or another acute neurological change
- persistent high fever with marked illness
- severe or worsening abdominal pain, jaundice or signs of liver or spleen involvement
- prolonged fever with breathlessness, fainting or known valve disease
- serious symptoms with a weakened immune system
Common Questions
Bartonella FAQ
Is it this cause
Is Bartonella the same as Lyme disease?
No. Bartonella bacteria and Borrelia burgdorferi cause different infections. They can occur in the same person, but one diagnosis does not prove the other.
Is Bartonella contagious between people?
B. henselae doesn't usually spread from person to person. B. quintana can spread indirectly when infected body lice move through close contact, shared clothing or bedding.
Can a cat bite cause Bartonella?
Yes. A cat bite, or an infected cat licking an open wound, can spread B. henselae.
Can a healthy cat carry Bartonella?
Yes. Healthy-looking cats can carry B. henselae in their blood, especially younger cats in some populations.
Can ticks spread Bartonella?
Researchers have found Bartonella in ticks and studied transmission in experiments, but have not shown that tick bites naturally infect people.
Is Bartonella curable?
Many Bartonella infections clear up or respond to treatment. The cure rate depends on the type: typical cat-scratch disease, neuroretinitis (eye), bacteremia (blood) or endocarditis (heart).
Testing
Should I test my cat for Bartonella?
Not to check whether your brain fog is Bartonella. CDC veterinary guidance doesn't recommend testing or treating a healthy cat for that reason. Flea control is more useful.
Are Bartonella stretch marks diagnostic?
No. Reports describe streaks like stretch marks, but ordinary ones are common, and a skin mark can't diagnose Bartonella.
Does a negative Bartonella test rule it out?
Not automatically. What a negative result means depends on the type of test, the sample, the timing and the suspected disease.
Treatment
Is there a Bartonella diet?
There's no proven diet that clears Bartonella. Food can still help you recover when illness or treatment affects appetite, weight or nutrition.
Sources
Key Sources
Cat-scratch disease encephalitis long-term outcomes, 2026. PMID 41544843
Neurobartonellosis review, 2024. PMID 39369199
B. henselae blood-vessel growth study with patient tissue, 2001. PMID 11553014
Bartonella bacteremia and adult psychosis association. PMID 38911703
Vasculitis and polyneuropathy case. PMID 17401716
Bartonella-associated cutaneous lesions study. PMID 33291688
Striae biopsy family investigation. PMID 23587194
Neuroretinitis review. PMID 39537838
Bartonella endocarditis diagnostic series. PMID 25540398
Molecular diagnosis and specimen comparison. PMID 35262411
High-risk bacteremia cohort. PMID 21996096
Serial Bartonella sampling study. PMID 23486720
Bartonella diagnostic review, 2025. PMID 41109599
Bartonella microenvironment treatment study (laboratory), 2026. PMID 42005843
Chronic B. quintana bacteremia randomized treatment trial. PMID 12821469
CDC Bartonella guidance. CDC Bartonella
Diagnosed: I'm on treatment and still have brain fog
Can brain fog last after Bartonella treatment?
Brain fog can last longer than the obvious infection symptoms. That does not automatically mean Bartonella is still active.
The infection can settle before the brain and nerves fully recover. In the 2026 cat-scratch encephalitis study, 8 of 19 people reported cognitive problems years later even though the overall neurological outcome was favourable. (1)
Poor sleep, nerve pain, dysautonomia, another infection or another cause can also keep cognitive symptoms going. In clinical practice, cognitive improvement can take 3-6 months or longer. That timing describes recovery. It does not set antibiotic length.
What can I do?
Today
- Prevent new flea, scratch, bite or body-louse exposure.
- Pick the symptom that needs its own action now: vision change, upright intolerance, broken sleep, severe pain or a treatment reaction.
- Check what improved, what didn't and what returned.
- Look at more than today's brain fog before you change treatment.
This week
- Know which Bartonella disease form your treatment targets.
- Ask how your doctor monitors that disease form.
- Work on any second cause of brain fog in parallel.
- Know whether a supplement has direct Bartonella evidence, host-cell evidence or only indirect evidence.
- If treatment changed nothing, recheck the diagnosis instead of automatically stepping up treatment.
What actually changes the outcome?
"Bartonella" is not a treatment plan. The disease form tells you what needs treating and what improvement should look like.
Typical cat-scratch lymph-node disease, neuroretinitis, persistent bacteremia and endocarditis are different problems. One daily thinking score cannot show whether all of them are improving.
Match the follow-up to the disease
Lymph-node disease
Is the node shrinking? Is the fever settling? Is the local illness resolving?
Eye disease
Vision and the follow-up eye examination matter more than whether the person's thinking feels clearer that week.
Bacteremia or endocarditis
Follow-up here checks your blood, heart valve and whole-body illness.
Brain fog
Watch it, but treat it as one outcome. Sleep, POTS, pain, medicines and another condition can keep it going after other Bartonella signs improve.
Prevent re-exposure during recovery
If a cat still has fleas, fix the flea problem. Reduce new scratches and bites. Keep cats from licking broken skin. If you have body lice, treat the lice, clothing and bedding. Treatment deals with the infection. These steps stop you catching it again.
What if other symptoms improve but brain fog remains?
If the rest of the illness improves but thinking does not, ask what can still be causing the thinking problems.
The nervous system may still be recovering. Poor sleep can keep concentration and memory impaired. Nerve pain can drain attention. POTS can make thinking worse upright. A medication can add cognitive side effects. Another infection or a separate brain-fog cause can still be present.
If swollen glands, fever or pain improved but upright symptoms did not, investigate the orthostatic problem. If sleep is still broken, investigate sleep. If a new medicine started before the cognitive change, review the medicine. If one symptom group never responded while the rest did, check for a cause other than Bartonella.
What if treatment helped and symptoms returned?
Symptoms returning does not tell you whether Bartonella returned.
These can look alike: a relapse, reinfection, bacteria left in one tissue, a different infection, another relapsing condition, or symptoms the first illness left behind. Bartonella can persist in specific settings, and published reports describe recurrent cat-scratch disease.
Recheck the diagnosis before repeating the old treatment. Ask what came back first, whether a test or exam finding came back with it, whether there was a new exposure, and whether the symptoms still fit Bartonella better than the alternatives.
Can Bartonella persist inside cells or biofilms?
Bartonella can occupy extracellular, intracellular and biofilm environments.
The 2026 lab study found important differences in antibiotic performance across those settings. Persistence inside cells or biofilms may make Bartonella hard to clear, even without antibiotic resistance. (24) Bartonella biofilm review, 2021
That's one reason confirmed complicated infections can be harder to clear than ordinary cat-scratch disease.
Can Bartonella treatment make you feel worse at first?
A Jarisch-Herxheimer-type reaction can occur with Bartonella treatment, but some symptom flares have other causes.
A sudden feverish reaction soon after treatment can fit a Jarisch-Herxheimer-type reaction. Weeks of worsening brain fog can have many other explanations. A treatment flare is not proof that Bartonella was the right diagnosis, and it is not proof that treatment is working.
Daily check
Treatment reaction check
Check what changes after treatment starts. A symptom flare can come from a treatment reaction, a medicine side effect, the illness itself or another problem.
Can another infection keep brain fog going?
One confirmed infection does not automatically explain every remaining symptom.
Human studies have found Bartonella together with Babesia and Borrelia. A 2024 molecular case series found Bartonella species in 6 of 7 people with confirmed Babesia odocoilei. A 2026 cohort of 50 people with long-term fatigue and neurological symptoms found Babesia in 12, Bartonella in 13 and both in 2. (21) (22)
These studies show that finding Bartonella doesn't rule out another infection.
What else can keep brain fog going after treatment?
If thinking problems linger, check every possible cause instead of assuming Bartonella is still there.
If treatment did nothing
No response is information.
There are several possible reasons. Bartonella may not have been causing that symptom. The test may have shown only past exposure. The treatment may have targeted a different form of the disease. Another infection or condition may still be active. Or recovery may take longer than clearing the bacteria.
Stay open to the chance that the evidence rules Bartonella out. If you didn't improve as expected, reconsider every possible cause.
What supplements have actual Bartonella research?
Some supplements used around Bartonella have direct laboratory evidence. Others have Bartonella-specific host-cell evidence or indirect evidence. Those are different claims.
Direct anti-Bartonella laboratory evidence
Cryptolepis
Cryptolepis killed stationary-phase B. henselae in a seven-day culture experiment.
Japanese knotweed
Many Bartonella herbal protocols use Japanese knotweed. It was active against both growing and non-growing B. henselae.
Chinese skullcap
Chinese skullcap showed anti-Bartonella activity, but was weaker than Japanese knotweed and Cryptolepis in the longer kill experiment. Reports describe rare liver injury.
Source: Botanical study
Bartonella-specific host-cell evidence
L-arginine
Bartonella can infect cells that help repair blood vessels. In a lab-dish study of human cells, L-arginine reduced the damage. It has never been tested in people with Bartonella. (3)
Indirect support
NAC
Bartonella can form biofilms. NAC can disrupt bacterial biofilms.
Curcumin
Bartonella activates NF-kB inflammatory signalling. Curcumin can suppress that pathway.
What should I bring back to my doctor?
Tell your doctor what changed, what did not, what returned and when.
- which symptoms improved first
- which symptoms never changed
- any symptoms that returned
- new cat, flea or other relevant exposure
- new swollen lymph nodes, skin lesions or eye symptoms
- whether brain fog is worse upright
- how sleep has changed
- treatment dates and medication changes
- previous Bartonella tests and which sample was tested
- confirmed co-infections or other diagnoses
"Some symptoms changed with treatment, but the brain fog is still significant. I want to work out if it's slow recovery, active Bartonella, a treatment problem, another infection or another cause. Here's what improved, what didn't and when."
Sources
Key Sources
Cat-scratch disease encephalitis long-term outcomes, 2026. PMID 41544843
Neurobartonellosis review, 2024. PMID 39369199
B. henselae blood-vessel growth study with patient tissue, 2001. PMID 11553014
Bartonella bacteremia and adult psychosis association. PMID 38911703
Vasculitis and polyneuropathy case. PMID 17401716
Bartonella-associated cutaneous lesions study. PMID 33291688
Striae biopsy family investigation. PMID 23587194
Neuroretinitis review. PMID 39537838
Bartonella endocarditis diagnostic series. PMID 25540398
Molecular diagnosis and specimen comparison. PMID 35262411
High-risk bacteremia cohort. PMID 21996096
Serial Bartonella sampling study. PMID 23486720
Bartonella diagnostic review, 2025. PMID 41109599
Bartonella microenvironment treatment study (laboratory), 2026. PMID 42005843
Chronic B. quintana bacteremia randomized treatment trial. PMID 12821469
CDC Bartonella guidance. CDC Bartonella
Supporter: I'm helping someone
What can Bartonella brain fog look like from the outside?
Brain fog can make someone forget conversations, lose track of plans, struggle with long explanations or become overwhelmed by decisions.
You may hear the same question twice. A plan discussed yesterday may feel new today. They may lose the point halfway through a conversation, or cope with one decision but stall when they face several at once.
What you may see
- needing information written down
- struggling when several people talk at once
- having a much better conversation at one time of day than another
What helps in the moment
Use one question at a time.
Go over the plan together. Separate what needs doing today from what can wait. For an important medical decision, ask whether they want another person there to help them remember.
Can Bartonella affect mood or behaviour?
Neurological Bartonella can include major mood or behaviour changes, but it's wrong to blame every angry episode, argument or psychiatric symptom on the infection.
Published neurobartonellosis cases include rage, panic, insomnia, personality change and psychosis. A 2024 blinded study found Bartonella DNA more often in adults with psychosis than in controls. This link does not show Bartonella explains psychiatric illness generally. (2) (4)
A sudden behaviour change is medically different when it happens with cognitive decline, nerve pain, visual symptoms, unusual skin lesions or another neurological finding.
Illness can explain behaviour without making harmful behaviour acceptable.
How can you help without taking over?
Go to appointments if they want you there
Brain fog makes it easy to forget the questions, what the clinician said and what happens next. Listen closely, review everything together afterwards, and let them lead.
Remember when things changed
Remember major changes: when their thinking shifted, treatment starts and stops, new medicines, major reactions, new nervous-system or vision symptoms and new exposures.
Reduce the number of decisions
Offer one choice at a time. "Do you want to deal with the appointment or the prescription first?" is easier than asking them to solve the whole week.
Help preserve the person's own account
Let them answer medical questions themselves when they can. If they lose the thread, help them return to what they were trying to say.
Help them test one explanation at a time
Useful support often means noticing which part of the problem you can test.
- If brain fog is worse standing, help record the upright symptoms.
- If sleep is awful, help get the sleep problem assessed.
- If one medicine lines up with the cognitive decline, put that timing on the medication list.
- If treatment helped pain but not brain fog, tell their doctor.
That is more useful than collecting dozens of symptoms into one Bartonella list.
What usually makes things harder?
Turning every good or bad day into evidence about active Bartonella can make the illness harder to understand.
- treating every symptom as Bartonella
- telling someone a treatment flare proves the medicine is working
- assuming a good day means the infection is gone
- assuming a bad day means the infection is active
- changing treatment based only on internet symptom lists
- dismissing psychiatric or sleep symptoms because an infection has been diagnosed
Notice what changed, and wait for the evidence before you decide the cause.
When does someone need faster medical help?
Dangerous behaviour, psychosis, seizures, severe confusion, sudden vision loss or another major neurological change needs urgent assessment regardless of the suspected cause.
- new major visual loss or a blind spot
- severe or worsening confusion
- fainting with serious illness
- persistent high fever
- severe abdominal pain or jaundice
- major breathing or heart symptoms
- rapidly worsening neurological symptoms
If someone may harm themselves or another person, use emergency services or the nearest emergency department. Get this help now, before anyone decides the cause.
Want the medical detail?
The Investigating path covers the evidence, testing, nerve pain, skin, eyes, transmission, differentials and treatment.
Sources
Key Sources
Cat-scratch disease encephalitis long-term outcomes, 2026. PMID 41544843
Neurobartonellosis review, 2024. PMID 39369199
B. henselae blood-vessel growth study with patient tissue, 2001. PMID 11553014
Bartonella bacteremia and adult psychosis association. PMID 38911703
Vasculitis and polyneuropathy case. PMID 17401716
Bartonella-associated cutaneous lesions study. PMID 33291688
Striae biopsy family investigation. PMID 23587194
Neuroretinitis review. PMID 39537838
Bartonella endocarditis diagnostic series. PMID 25540398
Molecular diagnosis and specimen comparison. PMID 35262411
High-risk bacteremia cohort. PMID 21996096
Serial Bartonella sampling study. PMID 23486720
Bartonella diagnostic review, 2025. PMID 41109599
Bartonella microenvironment treatment study (laboratory), 2026. PMID 42005843
Chronic B. quintana bacteremia randomized treatment trial. PMID 12821469
CDC Bartonella guidance. CDC Bartonella
References
- CDC Bartonella information
- Breitschwerdt et al., Pathogens 2020 - Bartonella Associated Cutaneous Lesions (BACL) in People with Neuropsychiatric Symptoms
- Bush et al., Parasit Vectors 2024 - Neurobartonelloses: emerging from obscurity
- Delaney et al., Front Psychiatry 2024 - Bartonella species bacteremia in association with adult psychosis
- Rolain et al., Antimicrob Agents Chemother 2004 - Recommendations for treatment of human infections caused by Bartonella species
- Xi et al., Virulence 2024 - Bartonella immune evasion mechanisms
- Yakubovsky et al., Int J Infect Dis 2026 - Cat scratch disease encephalitis outcomes
- Breitschwerdt EB et al., J Central Nervous System Disease 2019 - Bartonella henselae bloodstream infection in a boy with pediatric acute-onset neuropsychiatric syndrome
- Breitschwerdt EB et al., Pathogens 2025 - A one health zoonotic vector borne infectious disease family outbreak investigation
Related context
Food During Recovery
There's no proven diet that clears Bartonella. Food can still help you recover when illness or treatment affects appetite, weight or nutrition.
Use This Guide
Each path includes actions you can take now, what needs disease-specific medical treatment, and what to reassess if thinking problems remain.