Chiggers

A chigger -- also known as a red bug, harvest mite or Trombicula alfreddugesi -- is the larvae (not yet adult) form of a mite. Most chiggers are so small that they're not visible to the naked eye. Chigger bites cause redness, swelling and intense itching.


Causes/associated factors
Chiggers typically live in shrubby vegetation or grassy areas where soil temperatures are warm. If you brush against infested vegetation -- while camping, hiking, picnicking or fishing, for example -- chiggers may attach to your skin.
Chiggers often crawl up shoes or legs. Eventually, they attach themselves to skin covered by clothing -- especially near belts, straps or under elastic bindings. They tend to attach to tender or wrinkled skin, such as the backs of the knees, fronts of the elbows, ankles, armpits or groin. Chiggers may also attach to animals.

When chiggers bite, their saliva causes skin cells to break down and liquefy. If left undisturbed, chiggers may feed off the skin cells for about four days.

Chigger bites are most common during the summer and early fall.


Signs/symptoms
About three to six hours after a chigger attaches to your skin, you may notice intense itching. You may also notice a small red rash. If the chigger becomes engorged (filled with blood), it may look like a small red dot attached to a hair follicle. When the chigger falls off your skin, it'll leave a tiny red welt with a firm white center.
Symptoms usually last about a week, but may be present up to three weeks. The severity of your symptoms will depend on your particular sensitivity to the mite's saliva.


Diagnosis
The doctor will ask questions about your medical history and do a physical exam. The diagnosis may be confirmed if you have:
intense itching that began about three to six hours after possible exposure to chiggers
a small red rash
chiggers or harvest mites on your hair follicles

Treatment
The quicker the treatment, the better the results. Your doctor may suggest the following self-care measures:
Take a hot bath and scrub the bitten areas with soap to help dislodge the chiggers.

Soak the bitten areas twice a day with warm water.

Relieve the itching with calamine lotion, oatmeal baths or oral antihistamine medications. Carefully follow the label instructions and any precautions given by your doctor or pharmacist. Use hydrocortisone creams sparingly.

Wash all infested clothes in hot, soapy water.

Complications
Scratching the bitten areas may lead to a secondary infection that requires antibiotic treatment. In certain parts of Asia, chiggers may spread various diseases. Consult your doctor if you develop any signs of illness during or after this type of rash.

Pregnancy-specific information
Chigger bites appear to have no harmful effects for mother or baby. Remember to check with your doctor before using any medications while you're pregnant, including insect repellents.

Senior-specific information
Growing older is not a risk factor for chigger bites.

Prevention
Here are some steps to help prevent chigger bites.
If you'll be spending time outdoors in a vegetated area, wear high boots and pants made of a tightly woven fabric. Tuck your pant legs into your socks or boots.

When outdoors, use insect repellent containing DEET (N, N-diethyl-metatoluamide) on any exposed and intact areas of skin, as well as clothing cuffs, waists and sleeves. To prevent chigger bites, it's especially important to apply insect repellent to your shoes and lower pant legs. Follow the manufacturer's directions carefully.
Depending on the product, concentrations of DEET range from 4 to 100 percent. Products containing higher concentrations of DEET generally provide longer-lasting protection. Check with your doctor before using insect repellents if you're pregnant or breastfeeding.

The best approach is to use the lowest concentration of DEET effective for the amount of time spent outside:


30-percent DEET protects for six hours
24-percent protects for five hours
20-percent protects for four hours
6.65-percent protects for two hours
4.75-percent protects for an hour and a half
Even for children, DEET-containing products are the most effective insect repellents. The safety of DEET doesn't appear to be related to the concentration in the repellent. There are no studies on skin absorption of DEET in children, but studies of similar substances suggest that absorption through the skin wouldn't differ after age 2 months. Currently, 30 percent DEET is the maximum concentration recommended for infants and children older than age 2 months. Again, the concentration of DEET should be based on the time the child is expected to be outside. Keep insect repellent out of reach of children at all times, and don't let your child touch the repellent or apply it himself or herself. Discourage children from licking areas of skin treated with DEET. Kids often have a tendency to put their hands in their eyes and mouths, so discourage them from touching any skin treated with DEET as much as possible.


Avoid sitting or lying down in possibly infested areas.

After returning from the outdoors, take a hot bath or shower and scrub repeatedly with soap. This may help decrease the severity of symptoms if you've been bitten.

Wash possibly infested clothing in hot, soapy water (at least 125° F) for about 30 minutes before wearing again. Biting chiggers may remain in unwashed clothes or clothes washed in cool water.