Mosquito bite allergy
Mosquito bite allergies are informally classified as 1) the skeeter syndrome, i.e., severe local skin reactions sometimes associated with low-grade fever; 2) systemic reactions that range from high-grade fever, lymphadenopathy, abdominal pain, and/or diarrhea to, very rarely, life-threatening symptoms of anaphylaxis; and 3) severe and often systemic reactions occurring in individuals that have an Epstein-Barr virus-associated lymphoproliferative disease, Epstein-Barr virus-negative lymphoid malignancy,[2] or another predisposing condition such as eosinophilic cellulitis or chronic lymphocytic leukemia.
[3] The term papular urticaria[4] is commonly used for a reaction to mosquito bites that is dominated by widely spread hives.
Mosquitos belong to the biological order of Diptera (which includes all two-winged insects), suborder Nematocera, family Culicidea.
[6] In addition to mosquitoes, the Diptera order includes numerous other types of biting insects such as midges (e.g. sand flies) and gnats.
That is, not only climate but also cultural and socioeconomic conditions play critical roles in facilitating the development and prevalence of diverse allergic disease including mosquito bite allergies.
[6] About 2.5% of individuals (based on self reports)[6] show a "large reaction" in which the wheal is much larger than 10 mm (it may exceed 3 cm, i.e. 1.2 inches) in diameter and evolves into an extensive lesion that has black and blue discolorations due to subcutaneous bleeding, blistering, and/or necrosis.
Each of these recombinants causes immediate and delayed skin reactions when injected into volunteers with a history of mosquito bite reactivity.
T cells present in or recruited to the mosquito bite area appear responsible for mediating the full delayed reaction.
[6] Daily doses of a non-sedating second-generation anti-histamines (e.g. cetirizine or levocetirizine) can effectively reduce the immediate and delayed reactions to mosquito bites.
[6] Treatment of ordinary small or large mosquito bite reactions is limited to the use of non-sedative H1 antihistamines, e.g. cetirizine[6] or a drug with combined activity in inhibiting histamine and platelet-activating factor, e.g.
[9] Randomized, double-blinded, placebo-controlled studies are needed to determine if antileukotriene drugs or topical steroids have beneficial effects in reducing the symptoms of these bites.
[10] The bite site shows an intense, large reaction often resembling a cellulitis infection that persists for days to weeks.
[5] The syndrome usually afflicts healthy children, immune-deficient persons, and individuals who are new to an area inhabited by mosquito species to which they have not been exposed.
It involves sequential Type I, III, and IV hypersensitivity reactions[6] that are mediated by the IgE, IgG, and T cells that are directed against mosquito salivary proteins.
[11] The diagnosis of Skeeter syndrome is based mainly on the appropriate history of severe skin responses to mosquito bites that may be associated with fever.
The diagnosis can be supported by the detection, using for example an ELISA assay), IgE directed against mosquito saliva proteins in the afflicted individuals serum.
In addition to second generation, non-sedative H1 antihistamines, antipyretics and nonsteroidal anti-inflammatory drugs are typically used to treat patients with acute attacks of the syndrome.
[6] Individuals with systemic mosquito bite allergies respond to mosquito bites with intense local skin reactions (e.g. blisters, ulcers, necrosis, scarring) and concurrent or subsequent systemic symptoms (high-grade fever and/or malaise; less commonly, muscle cramps, bloody diarrhea, bloody urine, proteinuria, and/or wheezing;[3] or very rarely, symptoms of overt anaphylaxis such as hives, angioedema (i.e. skin swelling in non-mosquito bite areas), shortness of breath, rapid heart rate, and low blood-pressure).
[8] Individuals with certain Epstein-Barr virus-associated lymphoproliferative,[12] non-Epstein-Barr virus malignant lymphoid,[2] or other predisposing disease[3] also have an increased rate of systemic mosquito bite reactions but are considered in a separate category .
Other Epstein-Barr virus-associated lymphoproliferative disease reported to predispose individuals to mosquito bite allergies include Epstein-Barr virus-positive Hodgkin disease,[14] hydroa vacciniforme,[15] hemophagocytic lymphohistiocytosis,[16] aggressive NK-cell leukemia (also termed aggressive NK-cell leukemia/lymphoma),[14] and extranodal NK/T-cell lymphoma, nasal type.
[3] Rarely, however, it occurs in individuals who exhibit no signs or symptoms of a predisposing disorder but later develop chronic active Epstein-Barr virus infection.
[14] The allergenic proteins in the mosquito's salivary are thought to trigger the reactivation of EBV in the NK cells that are latently infected with the virus.
[13] The diagnosis of mosquito bite allergies in Epstein-Barr virus-associated lymphoproliferative disease depends on finding evidence of the lymphoproliferative disease, a compatible clinical presentation, and detection of EBV in the NK and T cells (e.g. T helper cells) in blood and/or mosquito bitten tissues.
Mild and clearly uncomplicated cases with, for example, indolent CAEV, are treated conservatively focusing on obtaining relief of symptoms such as skin irritation, fever, and malaise.
[2] Rare cases of systemic mosquito bite allergy have been reported to occur in individuals who have no apparent predisposing disease but later develop chronic active Epstein-Barr virus infection.
[17] Eosinophilic cellulitis, also known as Wells syndrome, is a rare skin disease usually occurring on the extremities and/or trunk that is characterized by episodic acute urticarial eruptions or erysipelas-like rashes which proceed to develop over the ensuing ~6 weeks into granuloma-like or morphea-like lesions.
However, there are reports that chronic lymphocytic leukemia patients can develop similarly severe skin reactions in the absence of an insect bite history.
