OVERVIEW

What is Paederus Dermatitis?

Paederus dermatitis is an inflammatory skin reaction caused by contact with the venom of Paederus beetles. Initially, it appears as dot-like, linear, or patchy redness and swelling, accompanied by itching or pain. Over time, clear blisters may develop, and in severe cases, pustules or even localized necrosis and blackening can occur.

If Paederus dermatitis is suspected, wash the affected area with soapy water before seeking medical attention. For minor lesions with mild symptoms, no treatment may be necessary—just close observation. Severe cases may require anti-inflammatory measures, wet compresses, or anti-infection treatments. Generally, it does not lead to serious consequences.

Does Paederus Dermatitis Occur Nationwide?

It is found in tropical and subtropical regions worldwide, and cases have been reported in many parts of China. While less common in northern regions, it still occurs occasionally.

What is a Paederus Dermatitis Outbreak?

Outbreaks of Paederus dermatitis have been reported, where multiple cases occur simultaneously in crowded areas, constituting an outbreak.

What Do Paederus Beetles Look Like, and What Are Their Habits?

Paederus beetles are black with yellow thoraxes or abdomens, resembling ants in size (about 3 mm). Their peak activity occurs in July and August. During the day, they hide in damp, dark places like grass, rice fields, or under rocks. They are nocturnal, phototactic, and often appear near light sources.

SYMPTOMS

What are the manifestations of Paederus dermatitis?

• Initially, there may be dot-like, linear, or patchy redness and swelling, accompanied by itching or pain.
• After some time, transparent blisters may appear, though they might not develop in all cases.
• In severe cases, pustules or even localized necrosis and blackening of the skin may occur.

Different symptoms may appear depending on the affected area. If unexplained blisters appear on the skin, especially in delicate areas (such as the eyelids, face, or perineum), seek medical attention promptly.

Will Paederus dermatitis on the eyelids affect vision in the future?

If the damage is limited to the eyelids, recovery will not affect vision. However, timely treatment is necessary to prevent infection.

CAUSES

What causes paederus dermatitis?

When exposed skin comes into contact with paederus beetles in summer, instinctive scratching or swatting can cause the beetles to release venom, damaging the skin. If the beetle is crushed, the venom may spread and further harm the skin.

Is paederus dermatitis contagious? Why do so many family members or classmates get it?

Paederus dermatitis is not contagious.

If others in the household also develop symptoms, they may have similarly come into contact with the beetle's venom. Although many people at school may contract it, the condition is not infectious. The likely reason is a high concentration of beetles near the school, combined with a lack of window screens in dormitories or classrooms, allowing the insects to come into contact with students. Therefore, there is no need to worry about transmission.

DIAGNOSIS

What tests are needed for paederus dermatitis?

If there are symptoms of high fever, it may indicate a secondary infection, and a blood test is needed to determine whether it is an infection. Seek medical attention promptly for paederus dermatitis, and specific treatment should be handled by a clinician.

Which department should I visit for paederus dermatitis?

For paederus dermatitis, you should promptly go to the dermatology department of a regular hospital. There is no need to be overly nervous, as it generally does not cause serious consequences. Avoid taking extreme measures such as amputation on your own.

Which types of dermatitis have symptoms similar to paederus dermatitis?

Some cases of insect bite dermatitis and contact dermatitis may resemble paederus dermatitis. Diagnosis depends on personal history, such as exposure to substances that cause dermatitis (certain chemical products like acids or alkalis can easily trigger contact dermatitis) or being bitten by insects (such as bed bugs).

TREATMENT

What self-treatment measures can be taken for blister beetle dermatitis before going to the hospital?

The affected skin can be washed with soapy water or a 1:5,000 potassium permanganate solution.

How is blister beetle dermatitis treated?

Blister beetle dermatitis rarely causes severe damage.

• Clean the affected area and avoid sun exposure after skin symptoms appear.
• If the damage is minor and symptoms are mild, no treatment is necessary—close observation is sufficient.
• If pain or itching is significant, a topical corticosteroid ointment can be applied in moderation until the lesions subside.
• For erosive areas, cold compresses with a 1:5,000 potassium permanganate solution can be used.
• If infection occurs, targeted antibiotic treatment should be administered.

All treatments should be discussed with a medical professional.

Does blister beetle dermatitis require hospitalization?

Most patients only exhibit skin symptoms (dot-like, linear, or patchy redness and swelling, followed by clear blisters. Unexplained blisters should prompt medical attention) and do not require hospitalization.

In rare cases, systemic reactions (fever, headache, nausea, etc.) may occur due to various reasons, necessitating hospitalization for observation and treatment.

How long does it take to recover from blister beetle dermatitis after treatment?

With treatment, recovery typically takes about two weeks. Some patients may experience residual hyperpigmentation, which often fades over time.

Are there side effects from using corticosteroid ointments for blister beetle dermatitis?

Due to the short duration of blister beetle dermatitis, side effects are unlikely.

Can blister beetle dermatitis heal on its own? What happens if left untreated?

Minor lesions may heal on their own in patients with good physical condition. Without infection, the lesions usually resolve within two weeks, leaving hyperpigmentation. Larger lesions (e.g., the size of an adult thumb) may not heal easily and could lead to infection.

Does blister beetle dermatitis leave scars?

Non-infected lesions typically leave hyperpigmentation. If infection damages the dermis, scarring may occur.

The skin consists of the epidermis, dermis, and subcutaneous tissue. The dermis has a complex structure, and damage to it is harder to repair, increasing the likelihood of scarring.

What should I do if hyperpigmentation remains after blister beetle dermatitis?

Hyperpigmentation usually fades naturally within 1–2 months and requires no special treatment. If it persists, consult a dermatologist or cosmetic specialist.

Is blister beetle dermatitis difficult to cure? Why do symptoms reappear shortly after recovery?

Blister beetle dermatitis is generally easy to treat. Recurrence is most likely due to renewed exposure to the insect's toxins.

What should I do if the skin remains red after treatment for blister beetle dermatitis?

If there is no discomfort, no further treatment is needed—the redness will fade over time. If discomfort persists, consult a doctor for evaluation and management.

What should I do if occasional itching occurs after treatment for blister beetle dermatitis?

This symptom is rare after treatment. If itching persists or recurs frequently, consult a doctor for assessment and appropriate measures.

Does blister beetle dermatitis spread?

With prompt treatment, it does not spread. Improper handling (e.g., blister fluid contacting other skin areas) may lead to spreading.

Are there any long-term complications from blister beetle dermatitis?

Blister beetle dermatitis is a common summer skin condition and usually leaves no lasting complications.

DIET & LIFESTYLE

Does Paederus Dermatitis Require Dietary Restrictions?

No dietary restrictions are needed, just focus on preventing wound infection. You can cover the wound with gauze. If blisters rupture, disinfect with iodine to prevent infection.

Will Paederus Dermatitis in the Genital Area Affect Fertility?

The toxin usually only damages the skin, and there are no reported cases of it affecting fertility.

Can Patients with Paederus Dermatitis Take a Bath?

Yes, as long as the wound is protected from infection. Cover the wound appropriately while bathing, and dry and disinfect it promptly afterward.

PREVENTION

How to Prevent Paederus Dermatitis?

• The best method is to use a mosquito net while sleeping;
• Eliminate all insects in the home;
• Clean regularly;
• Install window screens on doors and windows;
• Avoid grass and bushes during July and August.

How to Prevent Paederus Dermatitis Outbreaks?

Paederus dermatitis is more common in summer and autumn. These insects hide in weeds during the day and are mainly active at night. Therefore, actively remove weeds near living areas, install window screens in dormitories, and use mosquito nets on beds.

How to Properly Kill a Paederus Beetle? If Accidentally Crushed on the Body, Is It Effective to Immediately Wipe Off the Venom?

If a Paederus beetle lands on your body, do not crush or kill it directly on your skin. Instead, gently brush it off before killing it. Do not wipe off the venom; use tissue or a cotton ball to absorb it, and wash with soapy water. Removing the venom immediately may reduce damage, but minor harm might still occur. However, it is not fatal.

Some people have even resorted to self-amputation after developing Paederus dermatitis, which is completely unacceptable.