Chiggers
(Chigger Bites)

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Medical Author:

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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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.

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

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.