I use the oral horse paste only three times orally
I used the cattle pour on many times topically
The doctors don’t think it was ivermectin
My chatgpt says the same thing, it’s probably not what caused it, but just cautioning just to be safe
Long-Term Dermal Ivermectin Exposure and Parkinson’s Disease Risk
Background: Ivermectin Pour-On and Human Exposure
Ivermectin pour-on formulations (e.g. Norbrook’s Noromectin or Ivomec Pour-On) are topical liquids used in livestock (especially cattle) to kill parasites. They contain ivermectin, a potent antiparasitic macrocyclic lactone, usually dissolved in solvents like isopropanol for easy spreading on animal skin. These products are not intended for human use – in fact, labels explicitly warn: “NOT FOR USE IN HUMANS… This product should not be applied to oneself or others because it may be irritating to human skin and eyes and absorbed through the skin”. Despite precautions, farm workers can be accidentally exposed (e.g. via drips or splashes on their skin or face during cattle treatment). This raises questions about possible long-term health effects from repeated dermal exposure in humans. In particular, some pesticides and farm chemicals have been linked to Parkinson’s disease (PD), a neurodegenerative disorder. Here we investigate whether chronic skin exposure to ivermectin pour-on has any scientific association with developing Parkinson’s disease, and we review known toxicological risks (especially neurological effects) of ivermectin absorption through human skin.
Ivermectin Exposure and Parkinson’s Disease
Parkinson’s disease (PD) has been epidemiologically linked to certain pesticide exposures (notably some herbicides and insecticides) in farmers and rural populations. However, ivermectin is not among the pesticides associated with PD in the scientific literature. A 2015 toxicology study on pesticide transport and PD explicitly noted: “Although ivermectin has not been associated with Parkinson’s [disease]”, it was included only as a reference compound because of its known interactions with cell transport pumps. In contrast, pesticides like paraquat, rotenone, maneb, dieldrin, endosulfan, and certain organochlorines have been linked to increased PD risk in animal models or epidemiological studies. No comparable link has been found for ivermectin.
Despite extensive searching, no peer-reviewed studies or case reports were identified that connect long-term dermal ivermectin exposure to Parkinson’s disease in humans. Regulatory and toxicology reviews of ivermectin do not list PD or neurodegenerative illness as a risk. For example, while chronic high-dose ivermectin can cause other toxic effects (discussed below), Parkinson’s disease is not a known outcome of ivermectin exposure. This holds true even in large-scale human uses: ivermectin has been given orally to millions of people over decades (for onchocerciasis, scabies, etc.) with no indication of higher Parkinson’s incidence reported. In fact, rather than causing PD, some recent research has explored ivermectin as a potential adjunct treatment in PD models, since it can modulate neurotransmitter systems – ivermectin has “shown promise in facilitating L-DOPA treatment in preclinical models of Parkinson’s disease”. This experimental angle underscores that ivermectin is not recognized as a neurotoxin causing PD; if anything, it’s being studied for positive neurological effects, not for triggering neurodegeneration.
In summary, current evidence finds no link between chronic ivermectin exposure and Parkinson’s disease. Unlike certain farm chemicals, ivermectin is not considered a PD risk factor. No scientific publications or toxicology assessments connect “pour-on” use and Parkinson’s in humans. Any anecdotal concerns (for example, a farmer developing PD after years of using pour-on) have not been substantiated by research. The weight of evidence suggests that long-term dermal ivermectin per se does not cause Parkinson’s disease.
Toxicological Profile of Dermal Ivermectin Exposure
Although no Parkinson’s connection is known, ivermectin pour-on can pose other risks to humans if absorbed through the skin, especially at high doses or with repeated exposure. Ivermectin is highly lipophilic, meaning it can penetrate skin to some extent and enter the bloodstream. The product labels and safety data emphasize this: users are advised to wear gloves and avoid any skin contact because ivermectin readily absorbs through human skin and systemic effects may occur. Notably, a toxicology monograph states: “dermal absorption is appreciable and systemic effects may occur” with skin exposure to ivermectin. In other words, if you routinely get pour-on liquid on your skin (especially in large amounts), some ivermectin will likely enter your circulation.
How toxic is ivermectin via skin? Animal data show ivermectin is moderately toxic by dermal route: in rabbits the dermal LD_50 is about 406 mg/kg, placing it in Toxicity Category 3 (Toxic in contact with skin). This is far lower toxicity than some classic pesticides, but it’s significant – an accidental dousing in concentrate could deliver a harmful dose. Importantly, the solvent (often >60% isopropyl alcohol) can also irritate and dry out the skin with repeated contact. Manufacturer Safety Data Sheets note that prolonged or repeated contact with pour-on formulations may cause skin irritation, dryness and cracking. Direct eye exposure is a serious hazard as well: ivermectin solutions cause intense eye irritation, so splashes in the face/eyes must be flushed immediately.
There is no evidence of ivermectin causing chronic organ damage in humans at low exposure, but high-dose animal studies have highlighted some potential chronic effects. Notably, ivermectin is not mutagenic or carcinogenic in standard tests. The main “chronic” toxicity signal in animals has been reproductive/developmental effects at doses that also caused maternal toxicity (e.g. cleft palate in offspring of mice given very high doses). Thus, regulators classify ivermectin as a suspected teratogen (Reproductive Tox. Category 2), but this is only at high exposures. There isn’t evidence that long-term low-level exposure causes cumulative organ injury. Indeed, one product safety sheet notes that when used as directed on animals, “prolonged exposure of man is not expected” to occur, and no chronic toxicity is documented for casual exposure. Nonetheless, out of an abundance of caution, ivermectin’s general hazard classification includes “STOT RE 1” (Specific Target Organ Toxicity – Repeated Exposure, Category 1), indicating it can cause organ damage from prolonged high exposures. This classification is largely driven by high-dose studies (and covers sensitive targets like the nervous system and fetus at extreme doses), not ordinary incidental contact.
Neurological Effects of Ivermectin in Humans
Neurological side effects are a key concern for ivermectin exposure, since the drug acts on nerve signaling (GABA and glutamate channels). It’s important to emphasize that ivermectin usually does not cross the human blood–brain barrier in significant amounts. In healthy individuals, the P-glycoprotein (P-gp) efflux pumps in the brain’s capillaries actively eject ivermectin, keeping it out of the central nervous system. This is why ivermectin has a wide safety margin in humans and most mammals – at therapeutic doses it stays in the peripheral bloodstream and doesn’t reach brain neurons in high concentration. For the average person, even repeated normal exposures are unlikely to accumulate ivermectin in the brain. The remarkable safety record bears this out: after billions of human ivermectin treatments worldwide, serious CNS toxicity is exceedingly rare.
However, there are a few important caveats:
Genetic exceptions: A very small number of humans have genetic polymorphisms in the MDR1 (ABCB1) gene encoding P-glycoprotein. In these individuals, ivermectin isn’t pumped out of the brain as effectively. This mirrors what is seen in certain dog breeds (Collies) where a P-gp gene defect makes ivermectin lethal at normal doses. In humans, case reports are extremely rare, but one notable example is a 13-year-old boy treated with a standard ivermectin dose for scabies who developed coma and ataxia; he was found to have mutant P-gp genes causing a deficiency in drug efflux. Such cases are outliers, and neurological toxicity occurred because ivermectin penetrated the CNS abnormally. For the vast majority of people, this is not an issue – their P-gp keeps ivermectin out of the brain.
Massive overdose: If exposure is extremely high, the sheer concentration of ivermectin can overwhelm the barrier. Poisoning cases (often from misuse of concentrated veterinary products) demonstrate that very large doses can result in drug reaching the brain and causing acute neurotoxicity. For example, during the COVID-19 ivermectin misuse surge, poison centers saw cases of people ingesting livestock ivermectin. Symptoms included confusion, disorientation, weakness, ataxia (loss of coordination), seizures, and even coma in severe instances. In one series from Oregon, numerous patients who took huge veterinary doses developed altered mental status, balance problems, and one had a seizure. These symptoms emerged within hours of a large one-time dose. Essentially, an overdose can “force” ivermectin into the brain, leading to GABA-related depression of the CNS (somnolence, loss of consciousness) and potentially other neurological disturbances.
Loa loa co-infection: A special scenario unrelated to toxicity mechanism: in regions of Africa, people treated with ivermectin for parasitic disease who harbor heavy Loa loa worm infections can develop encephalopathy. This is actually due to an immunological reaction (massive release of dead microfilariae clogging cerebral microcirculation), not a direct toxic effect of the drug itself. It is a known risk in onchocerciasis programs, but not applicable to most people and not relevant to dermal exposure or Parkinson’s.
For typical exposures, the milder side effects of ivermectin are more common and transient. These include dizziness, lightheadedness, headache, tremor, and drowsiness – all of which reflect ivermectin’s slight pharmacologic action on the nervous system outside the brain or indirect effects (e.g. minor blood pressure lowering). Such symptoms have been reported occasionally even at normal oral doses for parasitic infections. They tend to be temporary and resolve as the drug is metabolized. If someone were repeatedly absorbing small amounts through the skin (say, a farmworker who gets a little on their skin frequently), they might experience subtle versions of these effects intermittently – for example, a bit of dizziness or fatigue after a significant exposure. Repeated facial exposure in particular could be problematic because the face has thinner skin and rich blood supply, possibly allowing more absorption. Also, contact around the mouth or nose could lead to accidental ingestion or inhalation of the liquid. This means a splash on the face could result in a higher systemic dose than the same splash on, say, a calloused hand (and it’s certainly more likely to irritate the eyes and mucous membranes).
Crucially, there is no indication that repeated low-grade ivermectin exposure causes any progressive or permanent neurological disease. There is no evidence for cumulative brain injury – ivermectin does not bioaccumulate in nervous tissue, and with intact blood-brain barriers it shouldn’t build up in the brain over time. Pharmacokinetic studies of daily ivermectin (for other indications) showed that steady-state levels are reached within a couple of weeks and do not keep rising with continued use. The drug is eliminated mainly in feces within days. Therefore, a farmworker with chronic intermittent exposure would likely have each small dose cleared before the next, rather than an ever-increasing internal level.
Bottom line for neurological risk: If a person gets a significant amount of pour-on on their skin or face on a given day, they could experience acute neurologic symptoms (drowsiness, dizziness, maybe nausea or ataxia) during the hours afterward, depending on dose. There have indeed been reports of “chronic” ivermectin toxicity in humans taking veterinary products daily for weeks, but interestingly those cases had milder symptoms than acute overdoses – typically just light neurologic effects – and they resolved when exposure stopped. No long-term neurologic damage was noted in those reports. Importantly, Parkinson’s disease (a chronic degeneration of specific brain cells) is not among the known risks from ivermectin. Unlike pesticides that kill dopamine neurons (like rotenone or paraquat), ivermectin’s mode of action doesn’t selectively destroy neurons; it mainly reversibly enhances inhibitory signaling. Consistent with this, the extensive human usage data have not flagged any increase in neurodegenerative illnesses. One review summarized that the “excellent safety profile of ivermectin after billions of treatments and minimal reported CNS toxicities” indicates serious neurological effects are highly unlikely except in extraordinary circumstances.
Repeated Facial Exposure Considerations
Special attention is warranted for repeated exposure on the face over years – e.g. a farmer often splashed in the face while pouring ivermectin on cattle. The face has several vulnerabilities: the eyes (very sensitive to irritation), the nose and mouth (entry points to internal absorption), and generally thinner skin. While no study specifically examines “repeated facial ivermectin exposure,” we can extrapolate from general knowledge:
Eye and Skin Effects: Chronic low-dose splashes on the face could cause dermatitis or rash over time, and repeated eye contact can lead to recurring conjunctival irritation or injury. Ivermectin pour-ons often contain isopropanol which can dry and irritate skin; over years this might cause redness or eczema on exposed facial areas. There are no reports of permanent eye damage from ivermectin, but each incident of eye exposure causes intense burning, tearing, and inflammation. Thus, someone routinely getting it near their eyes might suffer cumulative minor damage or chronic dry, irritated eyes.
Systemic Absorption: The area around the eyes, nose, and mouth has mucous membranes and rich capillary beds that could take up ivermectin more readily. For instance, if pour-on liquid drips around the nose or lips, some could be inadvertently inhaled or swallowed in tiny amounts each time. Over years, this pattern could effectively act like repeatedly ingesting small doses. While each dose may be too small to cause more than slight dizziness, one should consider whether this repetitive exposure could have any accumulating effect. Given ivermectin’s clearance, it’s unlikely to accumulate in the body fat or brain from such micro-doses beyond a steady-state. However, one unknown is whether years of low-level exposure could subtly affect the peripheral nerves or retina (since ivermectin in animals can affect GABA receptors in the periphery). No evidence of such chronic effects in humans has been documented. Safety monitoring of people on long-term ivermectin (e.g. prophylaxis trials) has not revealed neurological deficits – for example, patients taking 12 mg weekly for COVID-19 prevention over many weeks typically reported only occasional lightheadedness at most.
Parkinson’s Disease Concern: From a lay perspective, one might worry that “poisoning the nervous system a little over a long time” could lead to Parkinson’s. Scientifically, Parkinson’s disease is linked to specific toxic mechanisms (oxidative stress in dopaminergic neurons). Ivermectin has not been shown to cause those kinds of chronic changes. Repeated facial exposure would cause more general systemic exposure (affecting GABAergic signaling transiently) rather than targeted damage to dopamine cells. Additionally, epidemiological studies of farmers with chronic pesticide contact have pinned PD risk on certain chemicals – e.g. those that inhibit mitochondrial function in neurons – and ivermectin was not implicated. If ivermectin exposure were causing Parkinson’s in humans, it likely would have emerged in data from tropical regions where whole communities took ivermectin for river blindness for decades. No such pattern has been observed or reported in the medical literature.
Preventive Measures: All sources strongly advise using protective equipment to minimize chronic exposure, especially to the face. Wearing splash-proof goggles or a face shield and gloves when handling pour-on is recommended. If accidental contact to the face/skin happens, immediate washing with soap and water is advised to remove the chemical before significant absorption occurs. These precautions are prudent not because of any known long-term disease, but to prevent acute toxicity and irritation. By following these measures, even someone working for years with ivermectin pour-on should be able to avoid meaningful systemic absorption and any related neurologic effects.
Conclusion
After reviewing the scientific and medical literature, there is no evidence that long-term dermal exposure to ivermectin pour-on causes Parkinson’s disease in humans. Parkinson’s has well-established links to certain pesticides and toxicants, but ivermectin is notably absent from that list. Peer-reviewed toxicology data and regulatory assessments do not connect ivermectin with neurodegenerative outcomes. Cases of severe neurologic harm from ivermectin tend to involve acute overdoses or rare genetic susceptibility, not gradual poisoning.
That said, ivermectin pour-on is not benign: it can be absorbed through human skin and is toxic in sufficient dose. Known risks of significant dermal absorption include systemic ivermectin effects such as drowsiness, dizziness, tremors, or in severe cases seizures and coma (if exposure is very high). Repeated minor exposures might cause cumulative skin irritation and transient neurologic symptoms, but they have not been shown to produce any progressive neurological disease. The consensus from toxicologists is that ivermectin’s blood-brain barrier protection in humans makes chronic neurological toxicity unlikely. Indeed, ivermectin has been safely used in long-term regimens without evidence of Parkinsonian effects.
In summary, no research to date links cattle pour-on use of ivermectin to Parkinson’s disease, and the known human risks of pour-on exposure are limited to acute toxicity (neuro symptoms like confusion or ataxia during overdose), local irritation, and potential reproductive effects at high doses. Repeated facial exposure over years is undesirable and unsafe – it should be avoided via proper handling – but it has not been shown to trigger any latent neurological disorder.
Key Takeaways (Lay Summary)
No Link to Parkinson’s: There is no scientific evidence that getting cattle ivermectin on your skin over a long period will cause Parkinson’s disease. Researchers have found certain farm chemicals can contribute to Parkinson’s, but ivermectin is not one of them.
Known Side Effects: Ivermectin can affect the nervous system if a lot gets into your body, but usually it’s kept out of the human brain by natural protections. In normal use it’s very safe. Taking too much (or absorbing a large amount through skin) can make someone dizzy, sleepy, confused, uncoordinated, or in extreme cases cause seizures/coma. These effects happen quickly after a big exposure – and typically go away – rather than causing lasting brain disease.
Skin Absorption: Ivermectin can soak through human skin. Pour-on products are meant for cowhide, not people – they contain solvents that help the drug penetrate. So if you spill it on yourself, some ivermectin will enter your body. Repeated small exposures won’t accumulate indefinitely, but each dose could cause mild symptoms for a while.
Face Exposure: Getting pour-on in your face or eyes is particularly risky. It irritates the eyes and could be partly breathed in or swallowed accidentally. Always wear gloves and eye protection when handling it. If it splashes on you, wash immediately with soap and water. This prevents significant absorption.
Long-Term Outlook: People who have used ivermectin (even for years in medicine) have not shown higher rates of Parkinson’s or other neurologic diseases. The safest approach is still to avoid getting it on your skin altogether. Use precautions so you don’t have repeated exposure. But if you have had intermittent contact in the past, current research suggests it’s unlikely to cause any delayed neurodegenerative illness. Always prioritize safety to prevent any acute poisoning or irritation.
Sources: Peer-reviewed toxicology studies, drug safety data, and regulatory documents were consulted to prepare this report, among others. These confirm the absence of a Parkinson’s link and detail the known toxic effects of ivermectin in humans. All evidence indicates that, with proper handling to minimize exposure, ivermectin pour-on can be used around humans without long-term neurological harm.