Association between urticaria and nematode infections

Background: The association between parasites and urticaria was first suggested in the last century. A wide range, 0-75.4%, of the prevalence of parasitic infection has been reported with chronic urticaria (CU). Moreover, urticaria may be detected in patients with parasitosis. Nematodes are a type of helminth that infect hundreds of millions of people throughout the world. Objective: The aim of this work was to collect and review the published studies and cases of urticaria associated with nematode infections. Methods: A search of scientific literature data bases from January 1960 until May 2017 was carried out. Results: Numerous nematode infections have been associated with urticaria and/or angioedema: Anisakis simplex, Ascaris species (spp.), Dirofilaria spp., Enterobius vermicularis, Gnathostoma spp., Loa loa, Mansonella streptocerca; Necator americanus, Onchocerca volvulus, Strongyloides stercoralis, Toxocara spp., Trichinella spp., and Wuchereria bancrofti. The pathogenesis of urticaria in these infections generally remains unexplained. In some cases, skin manifestations were caused by the presence of the worm in the skin (Filaria, Gnathostoma); in other cases, such as A. simplex and S. stercoralis infections, there was a clear immunoglobulin E-mediated mechanism that led to allergic reactions, and infection and allergy coexisted; for other nematodes, the association was anecdotal and only a few cases were reported. Conclusion: It is difficult to detect a certain causal effect, except when urticaria improves or disappears after infection treatment. Cases of isolated urticaria not associated with other symptoms rarely may be caused by helminths. In the current guideline for urticaria, parasitosis is considered to be a rare possible cause of CU in developed industrial countries, Therefore, although a routine screening of parasitic infection in CU is not recommended, in our opinion, testing a patient with urticaria for parasites is a physician's choice based on the characteristics of the patient, such as associated symptoms, dietary habit, provenance country and previous travel.