Update on mosquito bite reaction: Itch and hypersensitivity, pathophysiology, prevention, and treatment

Abstract

Mosquito bites are endured by most populations worldwide. Reactions to mosquito bites range from localized wheals and papules with associated pruritus to rare systemic reactions and anaphylaxis in certain populations. The mechanism of itch is due to introduction of mosquito saliva components into the cutaneous tissue, although the exact pathophysiology is unclear. Histamine is thought to be a key player through mosquito saliva itself or through activation of mast cells by IgE or through an IgE-independent pathway. However, other salivary proteins such as tryptase and leukotrienes may induce non-histaminergic itch. Some individuals have a genetic predisposition for mosquito bites, and people with hematologic cancers, HIV, and other conditions are susceptible to robust reactions. Prevention of mosquito bites is key with physical barriers or chemical repellents. Treatment consists of second-generation antihistamines and topical corticosteroids. Further research on topical treatments that target neural-mediated itch is needed.

Keywords: genetic predisposition; hypersensitivity; insect bite; itch; mosquito; mosquito allergy; repellant.

Figure 1

Pathophysiology of Mosquito Bite Itch. Introduction of mosquito saliva components results in a number of local responses, three of which are proposed to cause itch: (1) the classic pruritic pathway involving histamine found in mosquito saliva binding to histamine receptors on sensory nerve endings; (2) an IgE-mediated hypersensitivity, in which IgE primed against mosquito saliva components crosslinks with mast cells, causing degranulation; and (3) modulation of the host immune response through IgE-independent and non-histaminergic pathways. Adapted from: Fostini et al. (29).

Figure 2

Skeeter Syndrome. The right flank of a middle-aged, male patient exhibiting Skeeter syndrome following a mosquito bite. This local area of redness and warmth was accompanied by fever. With previous episodes, he was given oral antibiotics from his primary care providers due to suspected cellulitis. This current episode responded well to topical corticosteroids and antihistamines.