Ivermectin side effects
Executive summary
Ivermectin commonly causes mild, transient symptoms such as itching, headache, dizziness, nausea, diarrhea and fatigue, while more serious reactions—especially neurologic events and severe allergic responses—have been reported but are rare and frequently tied to specific contexts or co‑factors [1] [2] [3]. Safety guidance from drug information and major health sites stresses that ivermectin is approved for parasitic infections and is not authorized for COVID‑19; misuse (including taking animal formulations) increases risk of harm [4] [5].
1. Common side effects: what most patients experience
Clinical reports and drug information list the most frequent adverse effects as pruritus (itching), headache, dizziness, gastrointestinal upset (nausea, diarrhea, abdominal pain), and fatigue or drowsiness, with pruritus, headache and dizziness specifically highlighted in pharmacovigilance analyses (pruritus 25.3%, headache 13.9%, dizziness 7.5%) [1] [2] [6].
2. Serious neurologic events: rare but documented
Pharmacovigilance and systematic studies have documented serious neurologic adverse drug reactions (sADRs) such as seizures, severe confusion, ataxia and other central nervous system problems after ivermectin use; dozens of suspected neurologic sADRs have been reported in global safety databases and case series, raising questions about mechanisms though these events are uncommon relative to total use [7] [1].
3. Allergic, ophthalmic and Loa loa–related reactions
Severe allergic reactions (anaphylaxis, hives, facial or throat swelling) and eye inflammation have been described and are listed as conditions requiring immediate medical attention; people with loiasis (Loa loa infection) or who have lived in areas where loiasis is endemic can have particularly serious reactions after treatment, including neurologic signs like seizures and visual symptoms [4] [5] [8].
4. Drug interactions and populations needing caution
Ivermectin can interact with other drugs and may have additive CNS effects when combined with medications that depress the nervous system; patients should disclose antidepressants, antipsychotics, benzodiazepines, anticonvulsants and other prescription or OTC agents to prescribers because concomitant medications were noted in safety reports and sometimes implicated in adverse events [1] [9]. Elderly patients and those with liver, kidney or cardiac problems require caution and monitoring because dose adjustments or increased surveillance may be appropriate [10].
5. Overdose, misuse and the COVID‑19 context
Overdose can produce severe gastrointestinal distress, breathing difficulties and neurologic toxicity including seizures and coma; regulatory and medical sources repeatedly warn against using veterinary ivermectin formulations or self‑medicating for COVID‑19, noting harms from inappropriate dosing and formulations intended for animals [8] [4] [5].
6. Limits of the evidence and how to interpret reports
Large‑scale community treatment campaigns and pharmacovigilance datasets provide signals of both common and rare harms but do not always establish causality—co‑medications, underlying infections (including onchocerciasis and loiasis), and incomplete reporting complicate interpretation, and some analyses call for improved ADR reporting in regions with less surveillance [1] [7]. Where sources differ, mainstream drug reference sites consistently present similar safety profiles and advise clinicians to weigh benefits for approved parasitic indications against known risks [3] [2] [6].
7. Bottom line: practical safety framing
For approved parasitic indications under medical supervision, ivermectin’s side effects are usually mild and self‑limited, but rare serious neurologic events, allergic reactions and complications in patients with loiasis or on interacting drugs justify prescriber vigilance and patient counseling; misuse, off‑label self‑treatment—especially with veterinary products—carries significant risk and should be avoided [2] [7] [4].