Chiggers also known as red bugs, harvest mite, scrub mite or bête rouge are not insects, rather they are close relatives of the arachnids, which include spiders and ticks. They belong to a specific family of mites called Trombiculidae. Chigger mites can be found worldwide; however in the United States only 2 species are bothersome to humans. In North America Eutrombicula alfreddugèsi (also called Trombicula irritans) is the most problematic.
The larval form of the chigger mite is extremely small, with an average body diameter ranging between 1/150 to 1/120 inches. Their small size makes them nearly invisible with the naked eye. The larvae are yellow, orange, or light red in color and have six legs compared to the adult, which are bright red with eight legs. It is the larval forms that are the culprits of chigger bites. The adult form is not parasitic. Chigger mites are typically found outdoors on low lying plants near tall grassy wooded areas or around water. They attach to clothing and migrate on the skin to look for an optimal feeding site. Contrary to most belief, chiggers do not burrow into the skin.
Chigger bites typically occur at sites on the body where clothing is worn tighter or in areas of skin folds. Some common sites are on the lower legs, ankles, behind the knees, waistline, groin, and axillae. Bites may go unnoticed until 1-3 hours later, after the mite secretes a digestive enzyme into the skin which kills skin cells. These dead skin cells form a tube called a stylostome which the larva uses to withdraw digested tissue. It is the presence of this enzyme that is responsible for intense itching. The itching is most intense in the first 24-48 hours then gradually subsides. Chigger dermatitis can present as a red flat or raised lesion. A vesicle or pustule may also be present. Resolution of chigger dermatitis can take up to two weeks to completely resolve.
Prevention of chigger dermatitis starts with wearing protective clothing. Long sleeve shirts, pants, thick socks, boots and/or high ankle shoes are most appropriate when spending time outdoors. Pants should be tucked into boots whenever possible. Mosquito repellants such as DEET can be sprayed onto skin and clothing, which also helps prevent infestation. Chigger mites are temperature sensitive and do not bit at the extremes of temperature. They do not bite if it’s colder than 60 F (15.5C) or hotter than 99 F (37.2C).
Treatment is aimed at controlling the intense itching associated with the bites. Topical lotions or creams applied to the affected areas, such as calamine lotion or corticosteroid creams aid in symptomatic relief. Oral Benadryl and other antihistamines are also of some benefit. Home remedies to "suffocate” the mite such as, applying clear nail polish, rubbing alcohol, or bleach are of no benefit since the mites do not burrow into the skin. Chigarid is a non-FDA approved topical treatment sold at many local pharmacies. It is a combination of camphor, phenol, and menthol.
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