Are Itch Mite Bites Dangerous?

The Full Story

Mites are arthropods and close cousins of spiders, scorpions, and ticks. There are thousands of mite species present in the world. Some mites, such as scabies mites, can cause severe skin reactions in humans.

The itch mites are members of the Pyemotes family of mites. Itch mites feed on the larvae or nymphs of insects that are found in straw, grain, and wood. They are found outdoors as well as indoors, and can even live in furniture that is infested with the mites. Female mites inject a toxic saliva into their hosts. This paralyzes the host and allows the mite to feed. Itch mite saliva is very potent and poisonous to their prey, and a single mite can paralyze and kill an insect larva or nymph that weighs 166,000 times more than the mite itself. Don’t panic though – the reactions when humans are bitten are not as serious! Although insect larvae represent the primary target of itch mites, the mites may bite humans when normal food sources are unavailable or when humans come into contact with infested areas. The bites are most likely to occur during late summer or early fall, when the itch mite populations are the highest. One species of itch mite, the oak leaf itch mite or Pyemotes herfsi, feeds on insect larvae that live on oak tree leaves. As oak trees are commonly found throughout the United States, outbreaks of itch mite bites affecting humans have occurred in multiple states including Kansas, Nebraska, Texas, and Oklahoma. In 2021, oak tree itch mites were suspected as the cause of an outbreak of itchy skin rashes that occurred in individuals living in the Washington, DC, area. The mites were likely feeding on cicada eggs and larvae that were present in the oak tree leaves, and fell from the trees onto unsuspecting people. Some people have surmised that the large number of Brood X cicadas that hatched in 2021 provided a larger food source than normal for the mites, causing the mite population to be larger than usual.

Human contact with itch mites results in a painless bite, followed by a skin reaction that is often extremely itchy. The itch mites are only 0.2 mm long and are not visible to the human eye. Because of this, people generally do not notice the bite when it occurs. Itching, which is often severe, develops 10-20 hours after the bite and evolves into a large and reddened area of inflammation that may measure more than an inch in length. Repeated scratching of the itchy area may lead to bacterial skin infections in some affected individuals. The rashes associated with itch mite bites may vary, and some may be accompanied by skin streaking. Affected individuals may also develop fevers, chills, or headache along with the skin reaction. In some cases, the itching and skin reaction may be confused with a spider bite or bed bug bites, and it can be difficult to distinguish itch mite bites from those of chiggers, mosquitoes, or other insects. A history of intense skin itching and redness, that occurs without a clear recollection of being bitten, is suggestive of exposure to itch mites. Cool compresses, topical steroids, and oral antihistamines (such as Benadryl®) can be used to treat the itching and skin rashes. Fortunately, the skin changes are self-limiting, and will often disappear within a few weeks.

It can be very difficult to avoid being exposed to itch mites when they are present in the environment.  The mites are miniscule in size and can be carried by the wind over long distances. They can pass through window screens and enter into homes. To protect against itch bite mites, it is recommended to wear tightly-woven clothing and to shower with soap and water after spending time in areas where mites may be present. The insecticide DEET may also help protect against the bites from some species of itch mites, although it is not 100% effective.

Kelly Johnson-Arbor, MD
Medical Toxicologist