What are common and serious side effects of ivermectin in adults and children?
Executive summary
Ivermectin’s common side effects in adults and children are typically mild and gastrointestinal or dermatologic — for example, diarrhea, nausea, itching, and skin rash — while more serious but rare effects include neurologic problems (confusion, seizures, ataxia, loss of consciousness) and severe allergic or hepatic reactions [1] [2] [3] [4]. Cases of severe neurotoxicity have been reported especially with overdose, inappropriate use (including veterinary formulations), or in patients with heavy Loa loa infection; hospitalization and even coma have occurred in such contexts [5] [6] [7].
1. Common, usually mild effects — the complaints you’ll see first
Clinical summaries and consumer drug guides consistently list gastrointestinal and skin symptoms as the most frequent complaints: nausea, diarrhea, abdominal pain, itching and skin rash; dizziness, headache and fatigue are also commonly reported [1] [2] [4]. Mayo Clinic dosing pages note that tablets are dosed by weight (200 mcg/kg for people ≥15 kg) and that side effects may be reported to regulators, implying routine monitoring for these typical reactions [8].
2. Neurologic risks — rare but serious and well-documented
Several peer-reviewed case series and reviews describe serious neurologic adverse events attributed to ivermectin including severe confusion, ataxia, seizures, depressed consciousness and coma. These events are rare in normal clinical use but have been observed with overdose, inappropriate self-medication, or when the blood–brain barrier is compromised [5] [6] [4]. Reports link higher risk to concomitant drugs affecting the central nervous system and to genetic or disease-related reductions in P‑glycoprotein function that permit greater ivermectin brain penetration [6].
3. When Loa loa and parasitic burden change the risk calculus
Available evidence shows that serious adverse events are more common in people with very high Loa loa microfilarial loads; encephalopathy and fatal outcomes have been reported in that setting after standard ivermectin dosing [3] [4]. Public-health literature and clinical reviews warn that the background parasitic disease burden can transform a usually safe antiparasitic into a cause of severe toxicity [6].
4. Overdose and inappropriate use — a public‑health problem during COVID-19 and beyond
Multiple articles and reviews document increased hospitalizations from inappropriate ivermectin use during the COVID‑19 pandemic, including use of veterinary products and excessive doses; symptoms reported in these cases include gastrointestinal upset, hypotension, decreased consciousness, seizures, and even death [5] [7]. The New England Journal of Medicine case descriptions emphasize confusion, ataxia, seizures and hypotension as presentations linked to misuse [5].
5. Children, pregnancy, breastfeeding — data gaps and cautions
Regulatory and clinical summaries emphasize limited pediatric data for children under certain weights (e.g., <15 kg) and note that appropriate studies are lacking for many youngest patients; some authorities caution about use in very young children because of a developing blood–brain barrier and potential CNS vulnerability [8] [3] [9]. Sources say it remains unclear if ivermectin is safe during pregnancy and note low secretion into breast milk but do not establish definitive safety [3] [10].
6. Liver, allergic and other systemic risks — less common but relevant
Drug information sources list allergic reactions (hives, facial swelling, breathing difficulty) as indications for emergency care and mention potential liver-related adverse events and transient renal findings in rare reports [11] [4] [12]. Consumer-facing sites urge patients to report side effects and to disclose concomitant medications because drug interactions can raise risk [11] [10].
7. Competing perspectives and limitations in the record
Clinical and regulatory sources presented here agree that common side effects are generally mild (nausea, diarrhea, itching) while serious neurologic events are rare but real [1] [2] [4] [6]. Some patient-education outlets stress mildness and utility for approved parasitic indications [1] [12]; academic reviews and case series emphasize toxic events when misused or in special contexts [5] [6] [7]. Available sources do not mention long‑term sequelae frequency in children after severe events — that gap limits conclusions about lifelong risks.
8. Practical takeaways for clinicians and families
Use ivermectin only for approved indications at weight‑based doses and under medical supervision; monitor for gastrointestinal, dermatologic and neurologic symptoms; seek emergency care for signs of allergic reaction or new neurologic deficits [8] [11] [4]. Public‑health reporting and case literature show that overdoses, veterinary product use, and treating unproven conditions (e.g., COVID‑19 outside trials) produce disproportionate serious harms [5] [7].
Limitations: this synopsis uses only the supplied sources; incidence rates and precise probabilities for each adverse event are not uniformly reported in those documents, and long‑term outcomes after severe neurologic events are not detailed in the provided material (available sources do not mention long‑term sequelae rates).