What are the side effects of ivermectin in humans?

1. Common, mild side effects — what patients usually experience

Clinical reference sites and patient-facing summaries list itching, skin rash, diarrhea, joint pain, dizziness, headache, vertigo and somnolence among the typical adverse effects seen with standard oral ivermectin dosing; topical forms can cause local reactions such as red or dry eyes and burning skin ^{[1] [2] [3]}. These sources portray these events as generally uncommon at the recommended human dose (about 200 µg/kg as a single dose), and they are the background set of complaints clinicians tell patients to expect ^{[7] [1]}.

2. Serious neurologic events — rare but real, and context matters

Peer-reviewed analyses and pharmacovigilance reports document serious neurologic adverse events — encephalopathy, confusion, stupor, coma — after ivermectin administration, especially in large-treatment campaigns in Africa and in patients heavily infected with Loa loa; mechanisms proposed include parasite‑related inflammatory responses and, less commonly, increased CNS penetration when P‑glycoprotein function is impaired ^{[4] [3]}. These events are described as rare but clinically significant and have a plausible biological basis tied to either parasite-load reactions or excessive central nervous system exposure ^[4].

3. Overdose and veterinary-product misuse — a major driver of toxicity reports

Multiple sources document that toxicity reports surged when people took veterinary ivermectin or doses far above human recommendations during the COVID-19 pandemic; case series show patients ingesting large amounts from animal pastes or solutions and presenting with neurologic symptoms, gastrointestinal upset, and musculoskeletal complaints — some required hospitalization ^{[5] [6]}. The New England Journal of Medicine case series and poison-center analyses specifically link hospitalizations to preventive or repeated high dosing and to veterinary formulations that are highly concentrated ^{[5] [6]}.

4. Special populations and genetic or infectious risk factors

Reporting emphasizes caution in young children, people with impaired blood–brain barrier protection, and in regions where Loa loa infection is endemic: the American Academy of Pediatrics and other reviews note limited safety data in children under 15 kg and warn of heightened CNS risk; separate epidemiologic work correlates pre-treatment Loa loa microfilarial density with post‑treatment neurologic risk ^{[2] [4]}. Additionally, genetic variants affecting P‑glycoprotein (mdr‑1) theoretically raise CNS ivermectin levels and neurotoxicity risk, a mechanism established in animal models and invoked in human case discussions ^[4].

5. Long-term or persistent effects — what reporting shows and what it does not

Available clinical literature and drug-information summaries describe acute and subacute adverse events but do not provide robust data on long-term sequelae from approved single-dose regimens; serious or fatal encephalopathy is reported rarely in specific contexts (Loa loa, overdose) rather than after routine use ^{[3] [4]}. Available sources do not mention systematic evidence of chronic long-term harms from standard, indicated human dosing outside those special circumstances (not found in current reporting).

6. Public-health takeaways and contested narratives

Sources converge on two clear public-health points: ivermectin is approved for human parasitic infections and topical conditions but is not FDA‑approved for COVID‑19 ^{[8] [9]}; and taking veterinary products or supratherapeutic doses increases the risk of toxicity and hospitalization ^{[5] [6]}. Reporting also shows a divergence in emphasis: clinical references stress safety at approved doses and list mostly mild effects ^{[1] [7]}, while toxicology reports and case series warn that misuse has produced serious neurologic harm and hospitalizations ^{[5] [6]}. Readers should weigh both perspectives and trust dose-verified, prescription human formulations administered under medical supervision.

Limitations: this summary is limited to the provided sources and does not attempt to adjudicate unpublished reports or literature beyond them; for individual medical advice consult a clinician and report suspected adverse reactions to public health authorities as recommended ^[9].