Versione Italiana


Luciano Schiazza M.D.
c/o InMedica - Centro Medico Polispecialistico
Largo XII Ottobre 62
cell 335.655.97.70 - office 010 5701818

Paederus dermatitis

Paederus dermatitis (also known as night burn) is a peculiar irritant dermatitis following the contact with an insect  belonging to genus Paederus and its fluid, which contains a blistering, toxic amide, the chemical pederin.

The dermatitis ischaracterised by erythemato-bullous lesions of sudden onset on exposed areas of the body: the neck was the most common site involved followed by the face. A periorbital predilection was present in 75 percent of the facial lesions.

On contact with the conjunctiva and/or cornea, Paederus sp. cause extensive painful peri-orbital swelling and purulent conjunctivitis known as Nairobi eye in Africa. Corneal erosions and blindness can follow. The effect of pederin is not immediately noticeable and only becomes apparent after 1 to 2 days. Dermatitis, often in elongate pattern (dermatitis linearis), is a result of slapping the beetle and crushing and smearing a Paederus against and across the exposed skin, with the following symptoms:

Paederus dermatitis
Paederus dermatitis

Paederus does not bite or sting, but accidental brushing against or crushing the beetle over the skin provokes the release of its coelomic fluid which contains pederin, a potent vesicant agent. The morphology and location of the dermatitis change from case to case but usually resembles the accidental dropping of a caustic or hot liquid. The uncommon association of acute dermatitis with minimal or no complaints (no associated painful sensations), the season and the case history facilitates diagnosis.

Pederin is a complex non-protein molecule, highly toxic, more potent than cobra venom. It inhibits protein synthesis and prevents cell division. Pederin (C25H45O9N) is an amide with 2 tetrahydropyran rings, and makes up approximately 0.025% of an insects weight (for P. fuscipes).

Structure of Pederin.

Structure of Pederin

Pederin does not seem to affect the palms of the hands or soles of the feet.  The delay in reaction to pederin and the insensitivity of feet and hands to this material make it more likely that peridin can be trasferred inadvertently (from clothing/bedclothes too) to other areas of the body (e.g., genital or periorbital areas,giving rise to “Nairobi Eye”). 

To mitigate and to avoid of speading  the effects of pederin to other body areas, immediately wash skin that has come into contact with a Paederus beetle with soap and water, or flush eyes with copious amounts of clean water. The dermatitis itself is not transferable. Paederus species belong to the insect order Coleoptera (i.e., beetles) (Gr. "koleos" = sheath; "pteron" = wing,) and the family Staphylinidae (short-winged beetles also know as "rove beetles"), subfamily Paederinae. Rove beetles are very common: they are the largest beetle family in North America (approximately 3100 species).They also occur in Africa, Asia, and South America.

Paederus beetles live in moist habitats : increased contact between people and these beetles may occur after rain showers and/or during a rainy season or an exceptionally wet year. Adults usually are 7-10 mm long and 0.5-1 mm wide, have a black head, posterior abdomen and elytra (this structure covers the wings and first 3 abdominal segments), and a red thorax and anterior abdomen in an alternating black-red-black-red-black, corresponding to head-thorax-elytra-anterior abdomen-posterior abdomen.


The adults are active during the day and are attracted by to light, perhaps more to artificial fluorescent light  at night (Paederus beetles do not seem to be as attracted to yellow incandescent lights). If windows or doors are left wide open, they may move into a house towards a light source  and  inadvertently come into contact with humans. 

Paederus are “skinny” enough to pass through many types of insect screening placed on windows and doors. Once in the house, they may land on a person, whether asleep or awake.  Rove beetles are harmless insects when in contact with the human body, if left unharmed. But if one try to kill or dislodge the insect by swatting crushing or smacking, it may damage it and cause the release and deposition of the insect body fluid  containing pederin on the skin.

Because of its irritant nature, pederin extract is also used as a self-medication for treatment of vitiligo in some parts of the world. Historically, extracts of Paederus beetles have been used by the Chinese since at least the year 739 in the medicinal treatment of boils, nasal polyps, and ringworm. It is an active predator of small insects and other arthropods, including pests of  several  crop-damaging insects food: for this reasond Paederus beetles often are beneficial to agriculture.

To prevent human/beetle contact it needs to prevent pederin-based trauma:

Because the lesion caused by Paederus is just a "irritant contact dermatitis", the reasonable approach is: