Dr. Stephanie Lareau whizzed through the trees on her mountain bike in Roanoke, Va., one day in 2018. When she wanted to stop for water and a snack, she didn’t think much of plunking down in a pile of leaves near a reservoir to rest.
The next day, Dr. Lareau found a cluster of red bumps along the waistband of her shorts. Her back started to itch intensely.
Dr. Lareau, an emergency medicine physician at Carilion Franklin Memorial Hospital in Virginia, had seen these marks once or twice before on patients. She knew what had caused them. They were from chiggers, a species of tiny, reddish-brown mites able to leave bites that remain itchy for days or weeks.
What is a chigger bite?
Chiggers are common in humid regions, like Southern and Midwestern states. Chiggers inhabit grasses, decaying leaf matter and low shrubs near bodies of water. Historically, chigger season in the United States has been from late spring to early fall. But this period is likely to expand as temperatures rise across the country, said Loganathan Ponnusamy, a principal research scholar in the department of entomology and plant pathology at North Carolina State University. He said that scientists in North Carolina were finding chiggers earlier compared with previous years.
After chiggers hatch, the larvae can cling to clothing or skin. Once on the skin, they secrete an enzyme to digest skin cells, said Dr. Avinash Patil, an associate professor of emergency medicine at Stanford University who is trained in wilderness medicine. The enzyme causes an immune response that can lead to skin irritation, itchiness and red bumps.
Hot spots for bites include folds of skin near tight clothing such as waistbands, the top of sock lines and the area behind the knees. (If you see red bites clustered around your waistband, you can assume they’re from chiggers rather than mosquitoes or other bugs, Dr. Lareau said.)
The larvae feed on human skin cells for a few days before falling off, Dr. Patil said. People may not realize they’ve been bitten until their bodies mount an inflammatory reaction. “By the time you’re itching, presumably, the chiggers are off,” he said. Peak itchiness often occurs 24 to 48 hours after a bite.
How do you treat chigger bites? And can you avoid them?
When spending time outdoors in moist, grassy areas in chigger-prone states — whether that’s a forest, riverbank or even your front lawn — experts suggest using insect repellent with DEET on your body and clothing. You can also wear long clothing, treat your clothes with the insecticide permethrin before wearing them and tuck pant legs into your socks to minimize skin exposure, experts said.
If you do get bitten, you can expect to be itchy for up to three weeks. Cold compresses can help with inflammation. Experts warned against excessive scratching to reduce chances of bleeding, scarring or secondary infection.
You can manage symptoms with over-the-counter remedies: oral antihistamines, calamine lotion and hydrocortisone cream. If you think you’ve been bitten, it’s also helpful to wash and dry exposed clothing on high heat, which effectively kills any chiggers that might have lingered on your clothes.
Some people mistakenly believe that chiggers burrow under skin for extended periods, and try home remedies like applying nail polish to “kill” mites, said Dr. Lareau. Chiggers will fall off on their own. Washing the skin won’t stop your body’s immune reaction if you’ve already been bitten.
What are long-term health risks? And when should you seek medical guidance?
Experts say chiggers in the United States pose minimal long-term risk. However, people should avoid scratching so bites don’t become open wounds susceptible to bacterial infection, which could require treatment with antibiotics, Dr. Patil said.
Chiggers are also common in regions including Southeast Asia, northern Australia and some Pacific islands. In these and other regions, chiggers have transmitted bacteria that can cause scrub typhus to people. No cases of disease transmission to humans have been documented in the United States.
“If you have been traveling abroad and you get chigger bites, they may be different than your chigger bites at home,” Dr. Lareau said. “That would be a time they definitely need to seek medical care.”