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Ivermectin Side Effects

Medically reviewed by Last updated on Mar 18, 2022.

In Summary

Commonly reported side effects of ivermectin include: fever, pruritus, and skin rash. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to ivermectin: oral tablet

Side effects requiring immediate medical attention

Along with its needed effects, ivermectin may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking ivermectin:

More common

  • Difficulty in moving
  • muscle pain or stiffness
  • pain in the joints
  • swollen, painful, or tender lymph glands in the armpit

Less common

  • Black, tarry stools
  • bloating or swelling of the face, arms, hands, lower legs, or feet
  • chest pain
  • chills
  • cold sweats
  • cough
  • dizziness or lightheadedness
  • dizziness, faintness, or lightheadedness when getting up from lying or sitting position
  • eye or eyelid irritation, pain, redness, or swelling
  • fast, pounding, or irregular heartbeat or pulse
  • feeling of constant movement of self or surroundings
  • fever
  • painful or difficult urination
  • rapid weight gain
  • sensation of spinning
  • shakiness in the legs, arms, hands, or feet
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swollen glands
  • tingling of the hands or feet
  • trembling or shaking of the hands or feet
  • trouble breathing
  • unusual bleeding or bruising
  • unusual sleepiness
  • unusual tiredness or weakness
  • unusual weight gain or loss


  • Agitation
  • back pain
  • bloody eye
  • blurred vision
  • change in consciousness
  • confusion
  • decreased awareness or responsiveness
  • difficulty in standing or walking
  • hallucinations
  • headache
  • irritability
  • loss of bladder control
  • loss of bowel control
  • loss of consciousness
  • mood or mental changes
  • redness of the eye
  • seizures
  • stiff neck
  • unusual dullness or feeling of sluggishness
  • vomiting

Incidence not known

  • Blistering, peeling, or loosening of the skin
  • burning, dry, or itching eyes
  • change in consciousness
  • confusion about identity, place, and time
  • dark urine
  • diarrhea
  • discharge, excessive tearing
  • light-colored stools
  • loss of consciousness
  • red skin lesion often with a purple center
  • sensitivity of the eye to light
  • swelling of the eyelids
  • tearing
  • upper right abdominal or stomach pain
  • yellow eyes and skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking ivermectin:

Symptoms of overdose

  • Confusion about identity, place, and time
  • decreased awareness or responsiveness
  • severe sleepiness

Side effects not requiring immediate medical attention

Some side effects of ivermectin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

  • Constipation
  • lack or loss of strength
  • loss of appetite
  • stomach pain
  • swelling or puffiness of the face

For Healthcare Professionals

Applies to ivermectin: compounding powder, oral tablet


Ivermectin is well tolerated compared to other microfilaricidal agents (i.e., thiabendazole, diethylcarbamazine). Adverse reactions (i.e., pruritus, fever, rash, myalgia, headache) occur commonly during the first 3 days after treatment and appear to be related to the extent of parasitic infection and systemic mobilization and killing of microfilariae. The majority of reactions can usually be treated with aspirin, acetaminophen and/or antihistamines. Adverse effects tend to occur with lesser frequency during periods of retreatment.[Ref]


Ocular side effects have included eyelid edema, anterior uveitis, blurred vision, conjunctivitis, limbitis, punctate opacity, keratitis, abnormal sensation in the eyes, and chorioretinitis/choroiditis; however, these effects are also associated with the disease onchocerciasis. Loss of vision has occurred rarely but usually resolved without corticosteroid treatment. Conjunctival hemorrhage has been reported during postmarketing experience in patients treated for onchocerciasis.[Ref]


Worsening of Mazzotti reactions, including arthralgia, synovitis, lymph node enlargement and tenderness, pruritus, skin involvement (including edema, papular and pustular or frank urticarial rash), and fever, has been reported during the first 4 days following treatment for onchocerciasis.

Nervous system

Nervous system side effects have included dizziness, headache, somnolence, vertigo, and tremor. Serious or fatal encephalopathy has been reported rarely in patients with onchocerciases, and heavily infected with Loa loa, either spontaneously or after treatment with ivermectin. Seizures have been reported during postmarketing experience.[Ref]


Gastrointestinal side effects have included anorexia, constipation, diarrhea, nausea, vomiting, and abdominal distention.[Ref]


Other side effects have included asthenia, fatigue, abdominal pain, chest discomfort, facial edema, and peripheral edema.


Hematologic side effects have included decreased leukocyte count (3%), eosinophilia (3%), and increased hemoglobin (1%). Hematomatous swellings associated with prolonged prothrombin times have been reported, but the clinical significance is unknown. Leukopenia and anemia have been reported in at least one patient.[Ref]


Hepatic side effects have included elevated ALT and/or AST. Elevated liver enzymes, elevated bilirubin, and hepatitis have been reported during postmarketing experience.[Ref]


Cardiovascular side effects have included tachycardia and orthostatic hypotension. EKG changes, including prolonged PR interval, flattened T waves and peaked T waves, have been reported in single cases. Hypotension (primarily orthostatic hypotension) has been reported during postmarketing experience.[Ref]


Dermatologic side effects have included pruritus, rash, and urticaria. Toxic epidermal necrolysis and Stevens-Johnson syndrome have been reported during postmarketing experience.


Respiratory side effects have included worsening bronchial asthma, laryngeal edema, and dyspnea.[Ref]


Musculoskeletal side effects have included myalgia.


Renal side effects have included rare transient proteinuria.[Ref]

Frequently asked questions


1. Greene BM, Pacque M, Munoz B, Taylor HR "Community-based treatment of onchocerciasis with ivermectin: safety, efficacy, and acceptability of yearly treatment." J Infect Dis 163 (1991): 381-5

2. Kumaraswami V, Devi U, Aziz MA, Ottesen EA, Sarma GR, Tripathy SP, Prabhakar R, Swaminathan M, Vijayasekaran V "Ivermectin for the treatment of Wuchereria bancrofti filariasis. Efficacy and adverse reactions [published erratum appears in JAMA 1988 Aug 5;260(5):640]." JAMA 259 (1988): 3150-3

3. Barbe RF, van der Lelij A, Wilson WR, Rothova A, Stilma JS "Side-effects of ivermectin in treatment of onchocerciasis." Lancet 1 (1989): 1439-41

4. Campbell WC "Ivermectin as an antiparasitic agent for use in humans." Annu Rev Microbiol 45 (1991): 445-74

5. Accorsi S, Awadzi K, Ba O, Giese J, Dadzie KY, Alley ES, Remme J, De Sole G, Karam M, Keita FM "Adverse reactions after large-scale treatment of onchocerciasis with ivermectin: combined results from eight community trials." Bull World Health Organ 67 (1989): 707-19

6. McTavish D, Clissold SP, Goa KL "Ivermectin. A review of its antifilarial activity, pharmacokinetic properties and clinical efficacy in onchocerciasis." Drugs 42 (1991): 640-58

7. Chijioke CP, Okonkwo PO "Adverse events following mass ivermectin therapy for onchocerciasis." Trans R Soc Trop Med Hyg 86 (1992): 284-6

8. Achumba JI, Ette EI, Thomas WO "Ivermectin: a long-acting microfilaricidal agent." DICP 24 (1990): 426-33

9. "Product Information. Stromectol (ivermectin)." Merck & Company Inc (2001):

10. Fayed H, Elmogy M, Marzok H, Rashad A "Oral ivermectin in the treatment of scabies." Int J Dermatol 38 (1999): 926-8

11. Ali HM, Bagi IA, Yousif MA, Bennett JL, el Sheikh H, Ghalib HW, Ismail A, Homeida MM, Williams J, Sulieman S "Prolongation of prothrombin time with ivermectin." Lancet 1 (1988): 1346-7

12. McNeeley MB, Richards FO Jr, Bryan RT, et al. "Ivermectin and prothrombin time." Lancet 1 (1989): 1139-40

13. Greene BM, Munoz B, Pacque MC, Taylor HR, White AT, Williams PN "Ivermectin and prothrombin time." Lancet 1 (1989): 1139-40

14. Sanmuganathan PS, Wijesundera MD "Ivermectin therapy in chronic strongyloidiasis." Trans R Soc Trop Med Hyg 86 (1992): 291

15. LeFichoux Y, Leotard AA, delGiudice P, GariToussaint M, Marty P, Bonnet H "Ivermectin in elderly patients." Arch Dermatol 135 (1999): 351-2

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.