Chiggers

Chigger is a common name for tiny mite larva (family Trombiculidae) whose feeding behavior and saliva causes intense, irritating itching in humans and animals. Only the chigger mites’ larval stage is parasitic. They prefer to feed on small mammals and birds but they do feed on humans. Later stages of chigger nymphs and adults prey on insect eggs and small arthropods like springtails (Koehler et al., 2022). Chigger mites are yellow to reddish in color but are typically too small to see without magnification (Koehler et. al., 2022).

Often Misidentified as Chiggers*

• red velvet mites
  (bygl.osu.edu/index.php/taxonomy/term/998)
• concrete mites
  (bygl.osu.edu/index.php/taxonomy/term/997)
• clover mites
  (ohioline.osu.edu/factsheet/HYG-2095)

*Larger common red mites are often seen on patios and lawn furniture, garnering attention and blame. They are not chiggers and do not bite humans, mammals or birds. They do stain clothing when squashed and can be accidental invaders found on windowsills and in homes.

QUICK TIPS

• Chiggers do not burrow into skin. This is a myth.
• Chiggers may become trapped in hair follicles due to swelling in response to their feeding.
• Chiggers do not suck blood. They feed on dissolved skin cells.
• Only the larval stage affects humans.
• Chiggers are very small (0.6–0.25 millimeters) and are often unseen by the casual viewer.
• Showering will remove the mite.
• The itching reaction can last up to 2 weeks or more.
• Itch is the result of your skin's reaction to the mite saliva and can vary person to person. Small red welts are common.
• Contact your physician or pharmacist to discuss symptoms, reactions, and treatment options.

Biology

Mites have unique lifecycle stages:

• egg
• pre-larva
• larva
• nymph
• adult

(Koehler et al, 2022; University of Maryland Extension, 2024)

The chigger larva is the pest stage and has six legs, and measures ¹/₁₅₀ of an inch (Missouri Department of Conservation (MDC), 2024). Chiggers develop eight legs, characteristic of all arachnids after molting from the larval stage into the nymph stage. Chiggers molt through three nymphal stages before molting into an adult that can reproduce. It can take several weeks for the cycle to complete. Temperatures and other weather conditions can affect development times (Koehler et al, 2022). Females can produce several generations a year resulting in high numbers of chiggers in the environment and a prolonged chigger season. However, the greatest numbers in Ohio are present in June through August.

Chigger mites overwinter as adults in soil and protected places. When temperatures rise above 60 degrees Fahrenheit, they emerge to mate and lay eggs. Preferred egg-laying sites include the humid soils of grassy fields, scrubby weedy areas, and lawns (MDC, 2024). Larval mites climb to the edge of grass blades or other plants, waiting to hitchhike on the legs of passing animals and humans. When we sit or play on the grass the mites can be attracted to CO₂ and dark clothing.

Once in contact with human skin, chigger mites seek out tight spaces where elastic bands and clothing provide shelter. Therefore, bites are often concentrated around the ankles under socks or shoe straps, near waistbands, under bra straps, and in armpits. Chigger bites rarely occur on open, uncovered skin. When bites occur in these open areas, they may be from mosquitoes or biting flies.

Feeding

Chiggers often begin feeding at the base of a hair follicle. They secrete salivary enzymes in order to dissolve skin cells into an ingestible form. Affected skin cells and saliva form a stylostome, a tube-like channel or straw, from which the larva sucks the digested skin slurry (Houseman, 2011).

Chiggers can feed for 2–4 days on their animal hosts, then they drop off to complete their lifecycle. On humans, the mites can become entrapped within the swelling tissue and die. The body of the mite can cause more inflammation of the skin. Most chiggers are knocked off through movement, scratching, or showering/bathing long before they can complete a meal. The itching reaction and welts can take several hours to develop and can last well beyond the mite's presence.

Promptly washing after being in chigger-infested areas can reduce feeding time and resulting itchiness. Since they do not burrow, wiping exposed skin with a washcloth or showering will help dislodge and remove chiggers (Koehler et al., 2022). Make sure to wash clothing on the hot setting to kill any remaining mites on exposed clothing (Kulhanek, 2023).

Prevention

Chigger mites do not feed for long and they do not burrow into skin or underlying tissues. The lingering itch is primarily due to a reaction to the mite’s saliva, but entrapped mites can intensify skin reactions. When dealing with chiggers, it is important to avoid folk remedies. Soap and water are sufficient to remove the mite. To deal with the itch, speak with a pharmacist or medical professional for recommendations on reducing itchy symptoms. Scratches caused by itching can become infected and should be attended to by a medical provider.

Preventing chiggers is recommended when entering possible mite zones. Use insect repellent such as DEET, picaridin, or lemon-oil-of-eucalyptus products and wear protective clothing to reduce your chances for any bug bite, including chiggers.

Chiggers thrive in humid, overgrown, grassy habitats, especially those frequented by small mammals and birds. In addition to home yards, they are found in transitional zones from fields to paths and scrubby growth to manicured landscapes. These scrubby areas may harbor chigger mites. Integrated pest-management solutions could include brush control, mowing lawns, and adjusting landscape features to increase sun exposure and air flow. These environmental changes make yards less inviting to mites and ticks.

To check your yard for chiggers, place a square of black paper or cardboard in the grass. Wait 10 minutes for mites to crawl onto the black surface. Against the black backdrop, the yellowish-red mites will be easier to spot (Koehler et al., 2022).

Insecticide is not generally recommended due to the risk of rebound populations. Remember, only the larval stage is a pest. However, targeted treatment of hot spots can provide short-term knockdown control. Bifenthrin or permethrin are two active ingredients in over-the-counter products. However, broad-spectrum insecticides pose a risk to beneficial predators and pollinators in the landscape (Waldvogel et al., 2015). To reduce impacts to beneficial insects, follow the label instructions carefully, do not apply where flowers are actively blooming, and avoid spraying when pollinators are actively flying. The label is the law for use and will also include important information about personal protective equipment needed, cautions for pets and children, and re-entry periods for people and animals. Other options can be recommended by lawncare or pest professionals.

Remember that other things can cause itching symptoms including poison ivy, mosquitoes, and skin allergies. People may be unaware that a skin reaction can develop from grass. Such reactions appear as tiny red welts on the open skin that came into contact with the turfgrass blades (Koh et al., 1997). Excessive scratching caused by any of these may lead to secondary infections at the site. Therefore, proper care and cleansing for severe itching can help, along with prevention.

Extension Staff are not medical professionals and cannot diagnose bites or other skin ailments. If you are experiencing itching or severe reaction to chigger feeding, consult a medical professional for appropriate care.

References

Gibbs, T. J. (2016). Chiggers [Fact sheet]. Purdue University Extension.
extension.entm.purdue.edu/publications/E-34/E-34.html

Houseman, R. M. (2011). Chiggers [Fact sheet]. University of Missouri Extension.
extension.missouri.edu/publications/g7398

Koehler, P. G., Oi, F. M., & Chaskopoulou, A. (2022). Chiggers [Fact sheet]. University of Florida Extension.
edis.ifas.ufl.edu/publication/IG085

Koh, D., Goh, C. L., Tan, H. T., Nge, S. K., & Wong W. K. (1997). Allergic contact dermatitis from grasses. Contact Dermatitis, 37(1), 32–34.
DOI: 10.1111/j.1600-0536.1997.tb00371.x

Kulhanek, A. (2023). What to know about chiggers. Buckeye Yard and Garden online, The Ohio State University.
 bygl.osu.edu/index.php/node/2210

Missouri Department of Conservation. (2024). Chiggers.
 mdc.mo.gov/discover-nature/field-guide/chiggers

University of Maryland Extension. (2024). Chiggers [Fact sheet]. University of Maryland.
extension.umd.edu/resource/chiggers

Waldvogel, M., Bertone, M., & Apperson, C. (2015). Mites that “bug” people [Fact sheet]. North Carolina State University Extension.
content.ces.ncsu.edu/mites-that-bug-people

This factsheet was originally written in 1998 by William F. Lyon.