Cicadas come with an itchy pest — tiny mites that can cause rashes

This year's cicada emergence was a double whammy of insects, with two groups of periodical cicadas that only come out of the ground every 13 or 17 years making a simultaneous appearance. But even after the two broods go back underground, it seems as though they may leave something pesky and itchy behind.

According to WebMD, cicada eggs are a food source for oak leaf itch mites — tiny arachnids that aren't even a quarter of a millimeter in length and that are "invisible to the naked eye." Each fall, several states have reported outbreaks of the pests, otherwise known as Pyemotes herfsi. They've been linked to cicadas before, with the Illinois Department of Public Health releasing a report in 2008 that said cicadas were the only insect parasitized by the mites the year prior. It was the first confirmed report of the mites terrorizing cicada eggs at the time.

"Brood XIII periodical cicadas emerged earlier in the year and laid large numbers of eggs in the terminal branches of many deciduous tree species in the outbreak area," the report says. "It appears that this abundance of cicada eggs served as the host upon which populations of P. herfsi mites amplified to outbreak levels."

In 2021, The Washington Post reported that some residents in the D.C. area were experiencing the mites after the cicadas left.

"We wake up at night just scratching," one woman told the Post. "...It's like we have splotches of white paint all over us now that we're using the calamine [lotion]. The sores are red and swollen, so it's not pretty."

In response to that article, University of Maryland Entomology professor Paula Shrewsbury said that the mites typically feed on midge fly larvae and that once they develop, "they drop from the tree...and can be carried by wind for large distances." From there, they'll drop down on people and animals and bite.

People are often exposed to the mites while near trees that have been infested with insects that the mites feed on or while dealing with fall foliage, she added. Unlike chigger bites that typically pop up  on the lower body around the waist or under socks and other tight clothing, bites from itch mites are typically around the neck, shoulders and chest, she said.

The latest cicada emergence seems to have brought them back.

"I think they're back and I don't know what to do about them," one TikToker said in June, showing a raised bump on her arm surrounded by a rashy-looking red area. "...It lasts forever. ... They are awful."

What to know about oak leaf itch mites

According to PennState Extension, these tiny mites are "elongated, reddish tan in color and have a shiny exoskeleton." Females are typically larger than males so they can carry up to 250 offspring at a time. Adult males will emerge from their mother's abdomen ahead of females, and once the females come out, the males will mate with them and then die.

The females will then find a gall, or a growth on a plant caused by mites, insects or some other kind of infestation. Any larvae in the gall are paralyzed with the mite's venom, which is strong enough to paralyze prey 166,000 times the mite's size, PennState Extension says.

Most people get these mite bites in the late summer and early fall when the species is most populated.

"Studies have shown that mites can fall from trees in numbers of up to 370,000 per day," PennState Extension says. "They are also easily carried by the wind and can potentially enter through window screens and thereby bite people who do not often go outdoors."

How to prevent oak leaf itch mite bites

PennState Extension says that eradicating the mites is difficult, as tree sprays usually don't seep into the galls where the mites hide out. Some people find that DEET is helpful, but the best mode of protection, the site says, is to limit time under infested trees and immediately wash clothes and shower after you are around those areas.

Symptoms can appear within 10 hours of exposure, Shrewsbury said.

"Bites may look like raised, red areas with a small central blister on the skin," she said. "The bites are itchy and may be painful if scratched."

How to treat oak leaf itch mite bites

Calamine lotions and itch creams can reduce the itching of the bites. Although it can be difficult, it's recommended not to scratch them, as it can lead to infection.