![]() For instance, the Zika, West Nile, Chikungunya, and dengue viruses cause a generalized maculopapular rash that is often itchy ( 14– 17). Secondary skin lesions due to scratching include excoriations which may obstruct primary skin findings, along with scarring and hyperpigmentation.įinally, the diseases transmitted by mosquitos and their treatments may also induce pruritus. In general, mosquito bite size is correlated to self-reported itch intensity ( 13). ![]() These individuals may be diagnosed with a mosquito allergy. Thus, it’s understood that natural desensitization to mosquito saliva may occur with long-term exposure ( 10), though a subsequent observational study noted marked individual variability in course of the stage progression with 6 of 10 patients remaining in stage III over a 30-year period ( 11).įor some individuals, a large local reaction (wheal > 5 mm) occurs within minutes to hours ( 12). Subsequent bites lead to first a delayed reaction only (stage II), then an immediate and delayed reaction (stage III), then an immediate reaction only (stage IV), and finally neither an immediate nor delayed reaction (stage V). The first mosquito bite in an individual results in a small, red spot (stage I). Mosquito bites in human skin progress through a series of stages determined by cumulative number of mosquito bites accrued during a lifetime ( 6, 9). These gradually disappear over the course of several days. The delayed reaction consists of pruritic papules of the same size which peak in 24-36 hours. Immediately after a mosquito bite, a round wheal 2-10 mm in diameter forms with surrounding erythema peaking in 20-30 minutes ( 6– 8). Mosquito bite responses occur in phases: the immediate reaction and delayed reaction, along with large local reactions in some individuals. The burden of mosquito-borne diseases is significant: 700 million infections leading to one million deaths every year ( 5). ![]() The diseases transmitted by mosquitos include malaria ( Anopheles) West Nile virus and western/eastern equine encephalitis ( Culex) and Chikungunya, yellow fever, dengue, and the Zika virus ( Aedes). Research has shown that mosquitos are particularly drawn to moist heat sources, exhaled carbon dioxide, and certain body odors ( 4). As they draw nearer to the host, they increasingly rely on thermal and olfactory stimuli. Mosquitos find their human or animal host via visual color cues, such as dark-colored objects ( 1, 3). Only female mosquitos bite humans, as blood provides the nutrients required to produce eggs ( 1). Feeding behavior varies with genus: for instance, Culex mosquitos are active mostly at night, whereas the Aedes genus is active during the day. There are over 3,500 species and subspecies of mosquito in 42 genera, three genera of which cause human bites: Anopheles, Culex, and Aedes ( 1, 2). Due to global warming, the incidence of mosquito bites is expected to increase as more extensive growth occurs. While the incidence of mosquito bites is unknown due to lack of reporting, the largest populations of mosquitos reside in humid tropical regions such as Thailand, Brazil, Indonesia, and the Philippines. Mosquitos are found in all continents except Antarctica ( 1). In some individuals, this local cutaneous reaction is exaggerated and debilitating, worsening the clinical course and decreasing quality of life, especially if mosquito bites are a common occurrence. Their bite causes a local cutaneous reaction leading to acute pruritus and the subsequent consequences of scratching: scarring, hyperpigmentation, and superinfection. Mosquitos are ubiquitous and are responsible for most insect bites worldwide ( 1). Further research on topical treatments that target neural-mediated itch is needed. Treatment consists of second-generation antihistamines and topical corticosteroids. Prevention of mosquito bites is key with physical barriers or chemical repellents. Some individuals have a genetic predisposition for mosquito bites, and people with hematologic cancers, HIV, and other conditions are susceptible to robust reactions. ![]() However, other salivary proteins such as tryptase and leukotrienes may induce non-histaminergic itch. 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. The mechanism of itch is due to introduction of mosquito saliva components into the cutaneous tissue, although the exact pathophysiology is unclear. Reactions to mosquito bites range from localized wheals and papules with associated pruritus to rare systemic reactions and anaphylaxis in certain populations. Mosquito bites are endured by most populations worldwide. Miami Itch Center, Dr Phillip Frost Department of Dermatology, University of Miami, Miami, FL, United States.Ashley Vander Does Angelina Labib Gil Yosipovitch * ![]()
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