Ever had a burn-like rash appear overnight? These rove beetles in Vietnam may be to blame

Many people in Hanoi have recently developed red, burning skin and blisters after coming into contact with rove beetles (Paederus).

N.T.H., 29, who lives in an apartment building in Yen Hoa Ward, Hanoi, woke up one morning to find a long red streak on the left side of her neck, accompanied by a burning sensation.

Initially, she thought her skin had reacted to cosmetics or an insect, so she simply washed the area and monitored it.

By that afternoon, several small blisters had appeared on the red patch, and the burning sensation had intensified.

The following morning, she discovered more red streaks on her arm and near her collarbone.

Some blisters had burst, causing pain and stinging when she showered or changed clothes.

After examining her, dermatologist Dr. Nguyen Tien Thanh said the symptoms were consistent with irritant contact dermatitis caused by toxins from rove beetles.

Rove beetles: A painful rash without a bite

Dr. Nguyen Huu Truong, deputy director of the clinical allergy and immunology center at Bach Mai Hospital in Hanoi, said many people wonder why they develop characteristic burn-like blisters despite never being bitten by an insect.

According to Truong, rove beetles do not bite or sting people.

Skin lesions develop when the skin comes into contact with toxin-containing fluid released from their bodies.

Rove beetles contain pederin, a toxin that can cause severe irritant dermatitis.

During the rice harvest or after storms and heavy rain, disturbances to their natural habitats may drive the insects indoors, where they are attracted to electric lights and may land on clothing, face towels, blankets or pillows.

"Many people instinctively slap or rub an insect when they see it crawling on their skin. This crushes the beetle and releases pederin, allowing the toxin to come into direct contact with the skin,” Dr. Truong explained.

"More dangerously, the toxin can stick to the hands and spread to the face, neck or eyes when people inadvertently touch those areas," Truong said.

According to Dr. Thanh, lesions typically appear 12-48 hours after exposure. The affected skin becomes red and burns, followed by the development of blisters or larger fluid-filled bumps.

The marks often resemble long whip-like streaks, patches or burns, and may appear on several parts of the body.

"Patients may notice blisters appearing in several places and assume the condition is spreading. In fact, this is not a contagious disease,” Dr. Thanh explained.

“The toxin can be transferred from one area of skin to another through contaminated hands or objects, or because several areas of skin were exposed to the toxin at the same time."

How to prevent exposure?

According to Dr. Thanh, rove beetles commonly live in rice fields, grasslands, gardens, and other humid environments.

At night, they are attracted to artificial lights and may fly into homes, particularly in residential areas near greenery, fields or construction sites.

Even apartments on higher floors are not safe from these insects.

Dr. Thanh advises people not to slap or vigorously rub rove beetles if they find them on their skin.

Instead, they should gently blow the insects away or use a piece of paper to remove them without crushing them.

If exposure to the toxin is suspected, the affected area should be washed with clean water and mild soap without scrubbing.

People should avoid scratching the lesions, popping blisters themselves or applying medications with unknown ingredients.

They should seek medical attention if the lesions spread, numerous blisters develop, the burning pain becomes severe, pus appears, redness or swelling worsens, or fever occurs.

If the toxin gets into the eyes, rinse them immediately with clean water or sterile saline solution. Avoid rubbing the eyes and seek specialist eye care.

To reduce the risk of exposure, households should install insect screens, avoid leaving doors and windows open when indoor lights are on at night, and check bedding, towels and clothing before use.

Doctors also warn that the rainy season is a period of increased rove beetle activity and reproduction.

In July 2024, Ho Chi Minh City Dermatology Hospital received an average of 50-70 patients a day at one point for contact dermatitis caused by rove beetles.

People living near areas with dense vegetation, grasslands or construction sites should take extra precautions during humid, rainy weather.

Residents should also keep their homes clean, paying particular attention to door gaps and damp, secluded corners where the insects may hide.

Maintaining good personal hygiene and avoiding leaving clothes out to dry overnight are also recommended.