Muller Journal of Medical Sciences and Research

: 2017  |  Volume : 8  |  Issue : 1  |  Page : 47--51

An outbreak of blister beetle dermatitis in a residential school: A clinical profile

Shibhani Sudheer Hegde, M Ramesh Bhat 
 Department of Dermatology, Venereology and Leprosy, Father Muller Medical Colege and Hospital, Mangalore, Karnataka, India

Correspondence Address:
Shibhani Sudheer Hegde
Department of Dermatology, Venereology and Leprosy, Father Muller Medical Colege and Hospital, Kankanady, Mangalore - 575 002, Karnataka


Background: Blister beetle dermatitis an irritant vesiculobullous disorder caused by rove beetles when it comes in contact with or is crushed on the skin. Their hemolymph consists of pederin, a potent vesicant responsible for the classical morphology of lesions. Materials and Methods: This was a descriptive study of 42 such cases was seen in a residential school, clinical details and photographs were collected using a standard pro forma and consent form, respectively. Results: Clinically, the lesions were present mostly on the uncovered parts of the body (81%). Due to the irritant nature of the lesions, flexures showed classical “kissing lesions.” Only 11.9% (5) cases reported a history of contact with the beetle signifying a high degree of suspicion to make the diagnosis. Conclusion: This article discusses one such outbreak with mention of the clinical profile and preventive methods of Paederus dermatitis.

How to cite this article:
Hegde SS, Bhat M R. An outbreak of blister beetle dermatitis in a residential school: A clinical profile.Muller J Med Sci Res 2017;8:47-51

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Hegde SS, Bhat M R. An outbreak of blister beetle dermatitis in a residential school: A clinical profile. Muller J Med Sci Res [serial online] 2017 [cited 2020 Dec 3 ];8:47-51
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Blister beetle dermatitis also known as Paederus dermatitis [1] or dermatitis linearis [2] is a seasonal vesiculobullous eruption caused by beetles of the order Coleoptera.[3] It is caused by three major families of beetles, family Oedemeridae, Meloidae, and Staphylinidae. Beetles of the genus Paederus belong to the family Staphylinidae (rove beetles) and is the largest of all three families.[4] These beetles do not bite or sting.[5] They mature in summer thus accounting for the seasonal incidence of such cases.[6] It is a peculiar irritant contact dermatitis characterized by sudden onset erythematous and bullous lesions on exposed areas of the body.[7] Crushing of the beetle or its accidental brushing against the skin leads to release of its coelomic fluid consisting of a potent vesicant called pederin.[8]Paederus beetles have been associated with outbreaks of blister beetle dermatitis in various countries including Malaysia, Australia, Sri Lanka, Nigeria, Kenya, Iran, Central Africa, Uganda, Okinawa, Sierra Leone, Argentina, Brazil, France, Venezuela, Ecuador, and India.[7] In India, although sporadic cases have been reported throughout the year, cluster of such cases are noted at the onset of rains.[4] We present a descriptive study of 42 cases of Paederus dermatitis in students of a residential college. The aim of the study was to study the clinical profile and factors associated with Paederus dermatitis noted in a dermatological camp held in a residential school nearby and to elicit factors associated with its occurrence and to raise awareness of this condition and preventive measures that can be used by the population.

Etiology and pathogenesis

The rove beetles belong to genus Paederus of family Staphylinidae, order Coleoptae, class Insecta and consist of 622 species of beetles that are distributed worldwide.[2],[9] Adults beetles are about 7–10 mm long, almost one and a half times the size of a mosquito. Structure consists of a black head, red thorax, upper abdomen, lower abdomen, and an elytral. Elytral is the structure that covers the wings and first three abdominal segments of the beetle.[10],[11] These beetles feed on debris and live in moist habitats.[12] Eggs are laid singly and develop to form larvae and adults in 3–19 days.[7]

Species commonly causing blister beetle dermatitis in India are Paederus melampus, in Venezuela are Paederus colombius and in South America are Paederus brasiliensis locally called as podo.[12] In a study conducted in Manipal, Paederus extraneus was reported.[4]

The beetles are nocturnal in nature and are attracted to artificial (incandescent and fluorescent) lights and thus come in contact with humans.[11]Paederus beetles do not bite; however, their hemolymph consists of pederin (latigaza),[13] a potent vesicant which is released when crushed on or brushed away from the skin. Pederin (C25H45O9N) is chemically an amide with two tetrahydropyran rings.[7]

The toxic principle in genus Paederus is pederin, pseudopederin, and pederon.[6],[14] Pederin is produced predominantly by the adult female beetle. Adult males and larvae store maternally acquired pederin or by ingestion.[15] A vesicant by nature, it blocks mitosis even at low levels probably by inhibiting DNA and protein synthesis without inhibiting RNA synthesis.[11] Epidermal proteases hence released could lead to acantholysis.[2]

 Materials and Methods

A sudden rise in cases presenting with redness and blistering mostly on the exposed sites of the body prompted a dermatological health camp to be conducted in a residential college. With 42 such cases seen in a day, clinical details and photographs were collected using a standard pro forma and consent form, respectively. All the patients were treated, and control measures were advised to the management, staff, and students of the institution to prevent further increase in number of cases.


A total of 42 patients were examined (13 males, 29 females) all in the age group of 15–16 years. All the students resided in the hostel blocks assigned by the school. The mean duration of symptoms was 4 days. All patients complained of fluid filled bustering rash at multiple sites with prior and/or associated complains of pain (78.6%) and burning sensation (73.8%). [Table 1] elicits the different signs and symptoms.{Table 1}

Thirty-four (81%) of them reported lesions on the exposed parts of the body; that is face, neck, upper and lower extremities. Twenty-five cases (59.5%) had lesions on the upper extremities followed by trunk in 28.6%, face 21.4%, neck 21.4%, and lower extremities 9.5%. The site wise distribution is given in [Table 2].{Table 2}

Around 21% of affected individuals reported a roommate with similar complaints and 28.6% (12) of them reported one similar prior episode that healed with postinflammatory hyperpigmentation. Other complications such as secondary infection and secondary eczematous change were noted. A total of ten patients (23.8%) had “kissing lesions” involving the flexures, for example, axillary, cubital, and popliteal fossae [Figure 1]. All patients responded satisfactorily to therapy given which included topical steroid cream for local application, antihistamines and oral antibiotics where the secondary infection was noted. Lesions healed within 1 week, in most cases. However, 28.6% (12) patients had residual hyperpigmentation. [Table 3] elicits different complications.{Figure 1}{Table 3}


Blister beetle dermatitis is a true irritant dermatitis of seasonal variability. Sudden onset of stinging and burning sensation followed by the appearance of fluid filled bustering lesions the next morning [Figure 2].[5] It has a worldwide distribution but is mostly reported from areas with hot tropical climate [4] usually at the onset of rains.[4]{Figure 2}

Paederus beetle belongs to order Coleopetra, family Staphylinidae. It is almost one and a half times the size of a mosquito.[10],[11] These beetles are active from May to July.[5] They breed in damp places and are attracted to artificial light.[6],[16],[17] Out of more than thirty species which can cause dermatitis, the important Indian species are Paederus fuscipes, Pulex irritans, Paederus sabaeus, etc.[5]

The earliest published record of blister beetle dermatitis is from Java in 1901 but was first described in East Africa by Ross in 1916. Since then these cases have been reported from all parts of the world.[4]

Blister beetle dermatitis classically affects exposed sites of the body such as extremities, face, and neck. Similar findings were noted in this study. Classically, a patient presents with an erythematous or oedematous plaque in a linear fashion (along the line of contact with pederin). Vesicles then develop in the center of this plaque. If history of contact with the beetle is present, the signs usually appear within the first 24–48 h of contact.[9],[10] Striking feature is the development of “kissing lesions” in the flexural surfaces where damaged skin comes in contact with the adjacent normal intact skin. Sites, where “kissing lesions” are usually noted, are the axillary, cubital, and popliteal fossae, but can also be seen in the adjacent surfaces of the thigh.[9]

Atypical variants can be seen in the form of diffuse erythema and desquamation in the face and upper body due to increased or recurrent exposure, due to underlying disorders like atopic dermatitis, or due to an immunological reaction resulting in the above mentioned clinical variant.[7] Genital or ocular involvement occurs secondary to toxins transferred from elsewhere through fingers. Unilateral periorbital dermatitis was seen in three patients of our study. Keratoconjunctivitis can be the other ocular manifestation also called as Nairobi eye.[2]

Blister beetle dermatitis should not be mistaken for liquid burns [Figure 3], other allergic or irritant contact dermatitis, herpes simplex, herpes, zoster, phytophotodermatitis, and millipede dermatitis.[2] Periorbital cellulitis should be ruled out especially during the initial presentation of periorbital blister beetle dermatitis.[18] A high level of suspicion is necessary to make a diagnosis of Paederus dermatitis. Hence, we propose the following criteria [Table 4].{Figure 3}{Table 4}

One major and two minor criteria are diagnostic of Paederus dermatitis.

Cases of blister beetle dermatitis should be managed as any other case of irritant dermatitis: removal of the enticing agent, washing of the exposed site with soap and water, application of cold compresses, use of a topical mild steroid cream to facilitate healing and antihistamines. If the primary lesions are infected, oral antibiotics may be added [Figure 4].[11]{Figure 4}

Recommended measures to prevent further outbreaks

Prevention of contact with beetles is the primary method of preventing Paederus dermatitis.[7]

Following recommendations have been made to prevent further cases of blister beetle dermatitis.

Health education regarding signs and symptoms of blister beetle dermatitis thus creating awareness Recognition of Paederus beetles and to avoid crushing these beetles against exposed parts of skin In suspected contact with the beetle, the area should to be washed with soap and water thoroughly Gentle removal of the beetle if it lands on the skin by blowing it off or facilitating it to move over a piece of paper Regular preventive sprays on land and use of insect repellents effective against these beetles (baygon 20% and malathion 50%)[5] Regular checking of rooms for presence of beetles, if present should be sprayed with insecticide and the carcass should be disposed safely by avoiding direct skin contact Removal of decaying vegetative matter around the establishments to prevent breeding of beetles Avoid use of artificial incandescent light that can attract the beetles Use of insect screens on windows and doors Safe distance of beds from the walls; use of a bed net Avoid manipulation of primary lesions and avoid rubbing of eyes after touching primary lesions.


Blister beetle dermatitis is a common condition, in the presence of public awareness and with a high index of suspicion, mucocutaneous exposure to pederin can be reduced.

Financial Support and Sponsorship


Conflicts of Interest

There are no conflicts of interest.


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