Toxic, Skin-Damaging, and Itchy! Beware of This Tiny Flying Insect When Taking Kids Out

During the summer and autumn seasons, some people may notice that upon returning home in the evening, their shoulders or necks suddenly develop a patch of striped rash blisters, accompanied by severe burning pain. They worry that it might be herpes zoster and seek medical attention, only for the dermatologist to reveal: This is paederus dermatitis!

Many people are still puzzled after being diagnosed, feeling that they have not been bitten by insects in this area. In fact, the occurrence of paederus dermatitis is usually not due to a direct bite from the paederus insect, but rather because the insect, attached to the human body or clothing under the street lights at night, is accidentally crushed by the person, and the insect’s body fluid comes into contact with the skin, resulting in a “burn” reaction similar to a chemical burn.

Therefore, understanding what paederus insects and paederus dermatitis are, and learning the correct way to deal with paederus insects, is the key to effectively preventing paederus dermatitis during the summer and autumn seasons!

What is a Paederus Insect?

Paederus insects are actually a collective term for a group of beetles belonging to the family Paederidae within the order Coleoptera, widely distributed around the globe with a multitude of species.

Common paederus insects have a slender body shape, with a body length of about 0.5-1 centimeters. The head, thorax, and the end of the abdomen are usually black, while the prothorax and the elytra covering parts of the mesothorax are often orange or yellow. The elytra are extremely short, only covering a small part of the anterior abdomen, and most of the abdominal segments are usually black and shiny, exposed, presenting a “hidden wing,” which is also commonly known as the “flying ant” among the populace.

Paederus insects prefer to live in damp environments and are commonly found in riverbanks, ponds, paddy fields, weedy areas, forests, park lawns, vegetable gardens, etc. They are usually active at night and hide in the shade during the day, such as under the leaves of plants or under rocks. They are strongly attracted to light and easily gather under street lights at night..

Paederus insects typically feed on small insects or decaying plants and animals and do not actively bite or suck blood from humans. Therefore, even if you encounter paederus insects at night, as long as you carefully drive them away, you will not be bitten by paederus insects causing dermatitis.

The main factor causing human disease from paederus insects is the venom they contain—paederin, which is primarily found in the body fluid of paederus insects and has strong irritancy and cytotoxicity, making it the main pathogenic factor causing paederus dermatitis.

This component is highly stable and can maintain its activity on the insect’s fragments, human skin surface, and even contaminated object surfaces for a relatively long time, so
it may cause contact dermatitis reactions in multiple areas after contact with the human body. However, the venom is non-volatile and can only function through direct contact, not through air transmission.

Therefore, even if you encounter a paederus insect, as long as you do not forcefully slap it and do not crush or break down the insect’s body, you will not cause a large amount of venom to overflow and contaminate the human skin.

What are the changes in paederus dermatitis?

If the skin does indeed come into contact with the body fluid of a paederus insect, the area of skin that is directly exposed to the fluid may exhibit striped, patchy, or linear erythematous changes within 2-24 hours, and the surface may have small papules, small blisters changes.

However, in the early stages of slapping, the rash is not immediately visible, and there is not much of a stinging reaction. So if you slap it just after, if you do not wash your hands in time, you may accidentally contaminate this part of the body fluid to other parts of the body, leading to the appearance of more rash areas beyond the slapped part.

Generally, when the rash is first discovered, there will be a relatively obvious severe burning pain or burning sensation, and the rash area will also have mild redness and swelling changes, followed by itching.

After 1-3 days, blisters may rupture, ulcerate, and exude fluid, followed by drying and forming dark brown or black scabs.

After another 1-2 weeks or even a longer period, the scabs slowly fall off, leaving temporary light brown or dark brown pigmentation spots, and a few severe cases may have superficial depressions . Pigmentation usually gradually fades within a few months.

✅ The factors affecting the severity of paederus dermatitis mainly include:

How to deal with paederus insects correctly?

Absolutely do not slap! Do not follow the traditional way of killing mosquitoes and flies to kill paederus insects! You can use gently shaking or use items carefully move away paederus insects, let it stay away from the human body.

If you accidentally crush the insect and suspect skin contact with venom, it is recommended:

✅  Rinse the affected area with plenty of running water for at least 5-10 minutes
as soon as possible!

✅ If soap is available, use soapy water to clean the area, this is the most effective way to reduce the concentration and damage of the venom.

For rashes that have already appeared, it is recommended to visit a dermatologist!

Dermatologists may adopt different diagnostic and treatment methods based on the condition:

Mild:

Mild erythematous papular urticaria acute phase treatment mainly involves cold compresses + topical calamine, weak potency corticosteroid ointments (e.g., hydrocortisone cream, desoximetasone cream) applied thinly for anti-inflammatory treatment.

Moderate to severe:

In cases of obvious edema, blisters, pustules, erosion, etc. moderate to severe rashes, they will 

● Routine wet dressing to converge exudative inflammation;

● Use antibiotic ointment to prevent secondary infection;

● After scab formation, use topical corticosteroid ointment for treatment.

● Oral antihistamines (e.g., cetirizine, loratadine) to relieve itching;

● Short-term oral corticosteroids (e.g., prednisone) for anti-inflammatory treatment;

● Oral antibiotics may be combined for treatment if secondary infection is obvious.

● Remove weeds, garbage, and rotten wood around the house, and keep the environment dry and tidy;

● Install screens on windows and doors (pay attention to the density of the screen mesh, ordinary mosquito net mesh may not be able to block), and ensure they are intact;

● Avoid piling up damp items indoors and outdoors;

●Try to keep outdoor lights away from doors and windows, or use mosquito repellent lamps/bulbs with longer wavelengths (yellow light, red light) (Paederus insects are less attracted to long-wavelength light).

● Wear long-sleeved clothes and pants, and tie the cuffs and ankles tightly;

● Avoid staying under lights for a long time (such as camping, cooling off);

● Avoid sitting or lying directly on the grass or the edge of the woods;

● Use mosquito nets(especially when camping).