To the Editor.—
The diagnosis of insect bite reactions is often difficult for the dermatologist, partly because of mimicry of other clinical conditions and because of the lack of history of recent contact with an appropriate arthropod. A history of contact is helpful, but a skin reaction is usually expected within 48 hours in genuine cases.The timing and severity of reactions to repeated insect bites depends on previous exposure. Mellanby1 showed that initial bites of Aedes mosquitoes produced little reaction, but, after repeated bites, a delayed reaction with an inflammatory weal occurs at about 24 hours. With further exposure, an immediate weal occurs that lasts for 2 hours and then disappears, to be replaced by the typical delayed reaction. With continuing exposure, subjects produce immediate reactions but no delayed response. Subjects who have had thousands of bites may eventually show no reaction at all.This pattern of reaction has been recognized to occur
Sansom JE, Reynolds NJ, Peachey RDG. Delayed Reaction to Bed Bug Bites. Arch Dermatol. 1992;128(2):272–273. doi:10.1001/archderm.1992.01680120148027
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