The outdoor pests commonly referred to as chiggers in North America are tiny red "harvest mites" of the genus Trombicula. They are best known for the red, itchy welts caused when their microscopic larvae feed on the skin cells of human hosts. They are also able to transmit the potentially deadly disease 'scrub typhus', but this is extremely rare in North America.
Chiggers are usually found in warm, damp areas with dense tree and scrub or tall grasses. Because females lay their eggs in a single location, the pest larvae will usually be concentrated. Chigger attacks can therefore be mistaken for a rash or hives in the likely event that many larvae attach themselves to a host simultaneously.
Chigger "bites" are generally not felt for 4-8 hours. The larvae do not actually bite, but use piercing mouth organs to attach themselves and inject a fluid that will dissolve skin tissue, which they then consume. This fluid and the body's immune response to it result in small red welts. Some people have an allergic reaction to chigger attacks that can magnify the symptoms or cause fever.
Contrary to popular belief, chiggers do not actually burrow inside the skin or drink blood, and they can be removed easily by bathing in hot, soapy water. Chiggers do not obtain adequate nourishment from humans, and will die quickly even if not removed. The welts, however, can last for up to two weeks.
Scratching of chigger welts should be avoided, particularly before the victim has had a chance to bathe, as this can move chiggers to other areas of the skin or to other people touched by victim. Overly scratching a welt or bite of any kind can also break the skin and result in infection.
Chiggers are attracted to warm, moist areas of the skin that are snugly pressed against clothing. Ankles, feet, groin, and behind the knees should therefore get special attention when bathing to remove chiggers. In children, armpits and waistbands may also be within easy reach of chiggers.
Chigger welts cannot be "cured", but the itching can be controlled with products containing antihistamines, such as hydrocortisol creams. If these are unavailable, any topical ointment that reduces the welt's exposure to air will usually provide some relief.
Chiggers can be avoided by wearing long, loose clothing that is tightly woven. Common insect repellents, including those containing DEET, are also effective. Promptly showering after returning from chigger habitat is strongly recommended, as this may remove any larvae before they can cause significant discomfort.
Though difficult, chiggers can be effectively removed from property by clearing the brush or mowing the grasses in which they live, or by using commercially available miticides and insecticides labeled for such use. These generally contain Cyfluthrin, Bifenthrin, Deltamethrin, or dusting sulfur. Read all labels carefully before use.