Numerous reports of rashes have been made to public health officials in areas of northern Illinois during the month of August. Similar rashes were reported in Kansas, Nebraska, Missouri and Texas during 2004 and those rash outbreaks resulted from bites from a species of the itch mite, Pyemotes herfsi. The same itch mite is also suspected as the cause of the Illinois rashes. The recent rashes have been described as red welts that look like chigger bites on the neck, face, arms and upper body; unlike chigger bites, they are not typically on the legs and don’t hurt when the bites occur. The bites are initially invisible but form into a pimple-like lesion after about 12 hours and can be present for up to two weeks. While oak itch mite bites do not pose a major health threat, they can cause intense itching; in addition, scratching can introduce germs into the skin which can cause infection.

Some questions and answers regarding the suspected oak itch mite bites in Illinois follow:

Why has it been so hard to confirm which mite is causing the rashes occurring in Illinois?  A lot of my neighbors are asking why not get an oak leaf and test it or sit under an oak tree?

There are more than 45,000 species of mites. Oak itch mites can cause leaf tissue to swell, resulting in a brown, crusty edge on the leaves (known as gall). But plant diseases and injury may produce gall as well. Oak leaves with this appearance are being collected and examined by expert entomologists. Mite populations in a location may vary with weather; other factors also affect the number of specimens available for collecting.

How did they determine this mite is the likely culprit?

Itch mites are suspected based on the lack of pain or visible insects on the skin before the welts occur, the appearance and location of the bites, the intense itching and the outdoor exposures of many of those who are affected.

My street has no oak trees yet everyone on my street has these bites. Why?

Although oaks are believed to be this itch mite's primary habitat, itch mites may have a range of habitats; also itch mites (which are wingless) can be blown some distance by the wind.

What are other possibilities for the causes of these rashes?

Some biting pests such as ticks and bed bugs produce painless bites. In addition to the oak itch mite, other species of mites may be capable of causing this syndrome.

If it is the itch mite, why don't I feel them crawling on my body?

The mite is extremely tiny (less than 1/125 of an inch with mouthparts that are only 1/700 of an inch long).

Many people have said that their bites seem to multiply overnight. Do the mites remain on the body unless we wash them off?

Mites may remain on the body for a few hours unless washed or brushed off.

Should I shower and wash every time I come in from outside if I'm in an area where itch mite associated rashes are occurring?

A hot shower, along with soap and the action of washing should get rid of the mites.
Clothes worn outside where itch mites are present should not be worn again until they are washed.

Can these mites live and reproduce in my home?

No. Without insect larvae to feed on, itch mites will die indoors within a few hours.

Are the bites dangerous for humans? 

Itchy welts on the skin are usually the only problem. Occasionally, individuals who are very sensitive, or have many bites, may develop fever, fatigue or nausea. Bites may become infected if germs are introduced into broken skin caused by excessive scratching.

Some people say the bites are itchier than any they've had before. How do you treat it?

The bites can be extremely itchy. Topical steroid creams such as 1 percent hydrocortisone cream should help relieve inflammation and may be purchased without a prescription at pharmacies. More potent steroid creams are available with a prescription. Antihistamines such as benadryl can also help reduce itching.

How long does the itching last?

Usually one to two weeks.

If bitten, are the young or the elderly at more risk for infection?

Not usually - the concern is to prevent infection from excessive scratching and this concern applies to all ages.

Why does it seem that even in the same household or on the same block, some people suffer more than others?

It is most likely that one person may encounter more mites than another person. This can vary due to the length of time they were outside, if the wind carried more mites to a certain location, the type of clothing a person was wearing, etc.

Any idea how long the itch mites will be around?

In Kansas, it was determined that itch mites were present until the temperature dropped below freezing. It is possible that other factors, like moisture, may affect how long the itch mites remain active.

Am I at risk of getting bitten whenever I go out?

In neighborhoods where people have developed this rash, or in areas where trees have oak leaf galls (brown, crusty edges on the oak leaves), it is wise to assume that itch mites may be present and take precautions.

What precautions can I take?

If you see brown, crusty edges on oak tree leaves consistent with the appearance of galls, be aware that mite activity is possible. Do not sit under or near these oak trees.

If you are in an area where you know itch mite associated rashes are occurring, or nearby oak tree leaves have brown and crusty edges: keep windows and doors shut from August through October, weather permitting, when "mite showers" can occur; remove clothing items worn outside and launder each day; and take a warm, soapy shower after coming indoors, especially after gardening, raking leaves or performing other outdoor activities.

August 2007