Dear Dr. Tim,

Every time I go out to pick raspberries I come home with chiggers. They itch like the blazes and especially so in very sensitive places. What are chiggers and why am I plagued by them?

Thanks, Itchy

Dear Itchy,

Americans should not have to tolerate rude behavior, especially from something as small as a chigger! And yet, that is just what we are exposed to every summer from May through September throughout the country. Chiggers are adolescent mites, so tiny that they are seldom seen. Several can actually fit on the period at the end of this sentence.

Most self-respecting mites feed on plants. It is only the teenage mites that bite people. Apparently, once they mature to adulthood, they grow out of their immature and obnoxious behavior of biting people, and live the rest of their lives feeding peacefully on plants.

Gangs of juvenile chiggers all have the following M.O. (modus operandi). They hang out on the tips of tall grasses, shrubs and weeds and wait to drop off onto any larger animal that happens to brush by. Usually these animals are birds, amphibians or small mammals but the mites are just as happy with the odd human that passes by. When chigger mites fall onto shoes or pant legs, they begin climbing in search of tender, moist skin to bite. They seem to concentrate in areas where clothing fits tightly against the body, such as around the ankles, groin, waist or armpits. This is exactly the rude behavior that I am talking about. A bite on an arm or back of the neck can be scratched in public. But public scratching of the groin, armpits or under the bra strap is an entirely different matter. It is socially unacceptable, politically incorrect and may even be illegal in some countries.

But, scratch you must. Once chiggers bite, there is no alternative. Chiggers do not burrow into the skin but rather pierce skin cells with their mouthparts and inject their special chigger saliva. This saliva contains enzymes that break down cell walls and causes the skin cells to liquefy. Meanwhile, human immune systems quickly react to this foreign enzyme resulting in, not only infuriatingly and intense itching, but also in the formation of a hard, red wall at the location of the bite. Chiggers capitalize on this body reaction by using the round wall, called a stylostome, as a straw to suck up their meals of dissolved body tissues, and then they promptly drop off. They are gone. They seem to never think twice about the trouble they have caused others. Meanwhile, the itching intensifies over the next 20 to 30 hours even though the mite is no longer present. Depending on the persons individual sensitivity and body reaction, itching may continue for days or even weeks.

So, what can be done? And probably most important, how does one stop chigger bites from itching?

Well, aside from amputation, physicians can sometimes prescribe an antiseptic/hydrocortisone ointment. This may help ease the itch and reduce chances of secondary infections caused by the itching and scratching, but it is not a perfect answer.

The best solution is prevention. Avoid getting into chiggers in the first place. Stay away from tall grasses and shrubs where chiggers are known to live. Chiggers love to live in brambles, as most people who pick black raspberries know or quickly learn. They also inhabit taller grasses close to the ponds and streams where bank fishermen stand. (Both raspberry pickers and fishermen can easily be spotted due to their obsessive scratching).

If you must go in those areas, tuck your pant legs into your socks and apply insect repellant containing DEET to the shoe and ankle area. This will stop many of the mites from gaining access to the skin and beginning their climb to areas where clothing fits tightly. (Theoretically, avoiding tight-fitting clothes or even going naked might help. If nothing else, it will certainly confuse the little biters not to mention friends and neighbors.)

I have found that if you know or suspect that you have been in chigger-infested habitats, take a hot, soapy shower as soon as possible. The mites are so small that it may take them several hours to crawl from shoes to where they want to bite, so you have plenty of time to wash them away. This is an effective prevention. Change your clothes and put the clothes you were wearing into the washer and dryer.

These methods are for the prevention of bites, but since you have already been bitten, happy itching.

Tim Gibb is a professor of entomology at Purdue University. He can be reached at gibb@purdue.edu

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SPINELESS WONDERS: Happy itching when chiggers feast on human flesh - pharostribune.com