Why do we develop allergic reactions to caterpillars and moths?
The Lepidoptera is an order of insects that includes moths and butterflies. The larval stages of these insects are called caterpillars commonly and are entirely different from their adult moth or butterfly forms, having a cylindrical body with a well-developed head, mandible mouth parts, three pairs of thoracic legs and from none up to five pairs of prolegs.
To defend themselves against predators, some caterpillars and moths have developed hairs and sharp spines that may be directly irritating or capable of transmitting various toxins.In most cases, direct contact with the offending species is necessary to provoke a reaction. Some hairs get lodged in the skin of human beings. Occasionally the irritating hairs can be detached and dispersed by winds, causing massive outbreaks of reactions in people. These hairs may also surround cocoons, eggs (transferred from the abdomen of female moths), or other environmental objects. Hairs from some species, such as the oak processionary caterpillar, are stable in the environment for at least one year.
Studies have found that some larvae's hairs contain histamine, which can raise small red bumps and cause itching and even pain when it comes into contact with human skin.
Histamine is produced by the human body to dilate blood vessels. Slight skin swelling can result. Histamine is also the substance that causes redness and itching in allergies and bug bites.
Some individuals may develop allergic reactions to particular species of caterpillars and moths.In very rare cases, spurs on the legs of giant insects can penetrate human skin and cause stings, dermatitis or urticaria. Rare species of moths, from the genus Calyptra, can bite human skin to feed on blood. Reactions range from mildly itchy, papular urticaria (small red bumps and swelling) that resolves within an hour; to moderately itchy, urticarial, scaly, blistering, or widespread eczema-like reactions that can persist for weeks.
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