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November 8, 2009
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Chiggers
(Chigger Bites)

Medical Author: Melissa Conrad Stöppler, MD
Medical Editor: William C. Shiel, Jr., MD, FACP, FACR

What are chiggers?

Chiggers are the juvenile form (larvae) of a certain type of mite of the family Trombiculidae. Mites are arachnids (like spiders and ticks).

Chiggers are found throughout the world. They most commonly live in forests, grassy fields, gardens, parks, and in moist areas around lakes or rivers. Most of the larvae that cause chigger bites are found on plants that are relatively close to the ground surface, because they require a high level of humidity for survival.

What do chiggers look like?

Chiggers are barely visible to the naked eye (their length is less than 1/150th of an inch). They are red in color and may be best appreciated when clustered in groups on the skin. The juvenile forms have six legs, although the (harmless) adult mites have eight legs.

Picture of Chigger Eggs, Larvae, Nymph, and Adult
Picture of Chigger Eggs, Larvae, Nymph, and Adult

How do chiggers bite humans?

Chigger mites infest human skin via areas of contact with vegetation, such as pant cuffs or shirt sleeves and collars. They migrate on the skin in search of an optimal feeding area. A common myth about chiggers is that they burrow into and remain inside the skin. This is not true. Chiggers insert their feeding structures into the skin and inject enzymes that cause destruction of host tissue. Hardening of the surrounding skin results in the formation of a feeding tube called a stylostome. Chigger larvae then feed upon the destroyed tissue. If they are not disturbed (which is rarely the case because of they cause substantial itching) they may feed through the stylostome for a few days.

The chigger's mouth and feeding structures are delicate and are best able to penetrate the skin at areas of wrinkles, folds, or other areas of skin that are thin. Most bites occur around the ankles, the crotch and groin areas, behind the knees, and in the armpits. Barriers to migration on the skin such as belts may be one reason that chigger bites also commonly occur at the waist or at other areas where their migration is prevented by compression from clothing.



Next: What are the symptoms of chigger bites? »

Chiggers: Effective Treatment

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