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Large local reactions to mosquito bites

John M Kelso, MD
Section Editor
David B Golden, MD
Deputy Editor
Anna M Feldweg, MD


Reactions to mosquito bites are caused by an immunologic response to proteins in mosquito saliva. Many people who are bitten by mosquitoes develop an immune response to these proteins; however, only a small proportion of them develop clinically relevant allergic reactions (most commonly large local reactions).

This topic briefly reviews the types of reactions that may result from mosquito bites [1]. It also focuses on large local reactions to mosquito bites and their clinical features, pathogenesis, natural history, diagnosis, differential diagnosis, treatment, and prevention. Other issues related to insect bites are reviewed separately. (See "Insect bites" and "Prevention of arthropod and insect bites: Repellents and other measures".)


Typical (normal) reactions — Local cutaneous reactions to mosquito bites typically consist of immediate wheals (swelling) with surrounding flares (redness) that peak at 20 minutes and delayed, itchy indurated (firm) papules that peak at 24 to 36 hours and resolve over the next 7 to 10 days.

The typical clinical course of sensitization and natural desensitization to mosquito salivary was described initially in the 1940s. It evolves over months or years in an individual (table 1) [2]. People who have never been exposed to a particular species of mosquito do not develop reactions to the initial bites from such mosquitoes. Subsequent bites result in the appearance of delayed local skin reactions. After repeated bites, immediate wheals develop. With further exposure, the delayed local reactions wane and eventually disappear, although the immediate reactions persist. People who are repeatedly exposed to bites from the same species of mosquito eventually also lose their immediate reactions. The duration of each of these five different stages differs, depending on the intensity and timing of mosquito exposure. These typical reactions are annoying, but not dangerous. The immunologic basis of sensitization and natural desensitization to mosquito bites was described in the 1990s [3,4]. Both immunoglobulin E (IgE) and immunoglobulin G (IgG), as well as lymphocytes, appear to be involved in the development of local reactions. Serum mosquito salivary gland-specific IgE and IgG levels correlated significantly with the size of the immediate skin reaction to mosquito bites, while lymphocyte proliferation to mosquito antigens correlated with the delayed reaction.

Large local reactions to mosquito bites — Large local reactions are by far the most common type of allergic reactions to mosquito bites:


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Literature review current through: Sep 2016. | This topic last updated: Nov 18, 2015.
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