Effect of ivermectin on allergy-type manifestations in occult strongyloidiasis

Background The immunomodulatory effects of helminths have been well described. However, there is a relative lack of literature regarding the link between parasites and allergic diseases. A number of patients with allergic symptoms have positive serologic test results for Strongyloides stercoralis. Objective To identify patients with allergy-type symptoms and coexisting Strongyloides infection and to analyze the effect of Strongyloides eradication therapy with ivermectin on these symptoms. Methods The medical records of our allergy clinic sites were reviewed for Strongyloides test results between January 2011 and October 2014. Each allergy-type symptom was assessed separately with regard to improvement after ivermectin therapy. Results Among the 1,446 patients who had Strongyloides serologic tests ordered, 127 (8.8%) had positive test results. Eighty-four patients had follow-up data regarding allergy-type symptoms after ivermectin treatment. Among these, 52 patients (61.9%) reported skin-related problems (pruritus, urticaria, angioedema, and/or rash). Forty-nine patients (58.3%) had asthma, and 73.8% had allergic rhinoconjunctivitis. Although respiratory symptoms typically did not respond to ivermectin treatment, 24 of 48 patients (50%) with skin symptoms reported a significant subjective improvement of symptoms after ivermectin treatment. Peripheral eosinophil counts significantly decreased after ivermectin treatment from 450 to 200/μL (P <.001). Conclusion Serologic testing for strongyloides may be indicated for patients with allergy-type symptoms and a suggestive exposure history. Patients with strongyloidiasis and primarily cutaneous symptoms experienced significant symptomatic improvement after ivermectin therapy.