If you have ever been bitten by chiggers you will not soon forget the red welts and intense itching that followed, even thought you probably never saw the chiggers themselves. “Chigger” is the name given to the tiny larval stage of the Trombiculidae mite. The adult mites are variously call harvest mites, red bugs, or scrub-itch mites. They are related to ticks and spiders and, like them, the mite’s life cycle has four stages: egg, larva, nymph, and adult. Nymphs and adults Trombiculidae mites are not parasitic. In fact, they benefit us by eating the eggs of several insect pests. The adults can winter over, even in cold climates, and they lay their eggs in the early spring. A larva emerges from the egg, and it is this larva that is called a chigger. A single summer can see several generations of the mite. A chigger is almost microscopically small. A magnifying glass is usually required to observe it although sometimes clumps of the tiny orange-red larvae can be seen with the naked eye. After the chigger emerges from it’s egg, it climbs to the top of nearby vegetation and waits for a host to come along so it can attach itself and begin to feed. Common hosts are rodents, rabbits, birds, snakes, toads, and many mammals- including humans.
The chigger bite
When a chigger attaches to it’s host, it moves quickly to a feeding site. It prefers areas under tight-fitting clothes. Under socks is probably the most common site, but it also likes to settle beneath waistbands or bras. Another favorite site is in skin folds. Once attached to the host, the chigger pierces the skin and injects a fluid (a digestive enzyme) into the bite. This enzyme begins to liquify the cells of the surrounding tissue and this is what the chigger feeds on. It is not a blood feeder as some believe, but feeds on the host’s emulsified tissue. The damaged tissue surrounding the bite hardens and actually forms a straw-like channel, called a stylostome, that allows the chigger to dine on deeper tissues than it can physically reach. The hardened tissue is the primary source of the inflammation and intense itching caused by chigger bites. The site of the bite develops a red welt and sometimes a rash. Itching is a delayed reaction and does not start when the bite first occurs, instead it starts after enough time has passed for the enzyme to damage the tissue around the bite. The itching will begin at least several hours after the bite and sometimes not until 24 to 48 hours later. Untreated, the itching will last for a week or two but even without treatment it will usually heal on it’s own. In the United States chiggers are not known to transmit any disease although species of Trombiculidae mites found in Japan and Southeast Asia do transmit a serious disease called scrub typhus.
There are several common misconceptions about chiggers. The orange-red color of the chigger leads some to believe that they suck the host’s blood, but as already noted they do not. Another misconception is that they burrow into the skin of the host. This is also incorrect. The tiny chigger sometimes appears to have burrowed, but actually the damaged tissues are so inflamed that they surrounded it.
Treating chigger bites
The treatment for chigger bites is focused on alleviating the discomfort and intense itching. If you develop welts at the bite sites, the itching can be reduced by covering them with vaseline, lotions or creams, or oils. These work by limiting the bite site’s exposure to air which aggravates the itching. The treatment is even more effective if the substance used contains an antihistamine or local anesthetic to further reduce the itching. Calamine lotion, caladryl, and hydrocortisone ointments or creams may all offer some relief. If you know that you were in an area infested with chiggers, take a hot bath or shower and soap yourself several times to dislodge any unwelcome guests. By removing them quickly, you can minimize the effect of their bites. Your clothes should also be laundered in hot water. Cold water will not kill them and you can be reinfected the next time you wear the clothing.
Although the chigger does not transmit disease (except as previously noted), the bite site can develop a secondary infection- usually because of heavy scratching. For this reason, the use of a topical antibiotic may be a useful preventative measure. Be sure to see a medical professional if the bite becomes infected. Rarely, someone may have severe allergic reaction to a chigger bite. Immediate medical attention is recommended.
How to avoid chigger bites
The best way to handle chigger bites is to avoid them. When outdoors, avoid likely chigger habitats. Stay on roads and paths when possible. If you must walk through high grasses, weeds, etc, wear long pants and sleeves. Tuck the pant legs inside your boots and keep sleeve cuffs buttoned. Repellents are effective but only for a few hours before they must be reapplied. Look for products containing either DEET or Permethrin. Be sure to follow the product instructions carefully to avoid adverse reactions. Never wear pet flea collars on your ankles. This can result in serious chemical burns and the active ingredients in the collars are toxic.