Paederus dermatitis (PD), is an irritant contact dermatitis, which is common throughout the world but more so in hot humid tropical and subtropical places. It is caused by Paederus or rove beetles [1]. The Paederus group of insects belongs to the Staphylinidae family, order Coleoptera [2]. Paederus beetles are nocturnal in nature and draw themselves to incandescent and fluorescent lights [3]. when this beetle is crushed accidentally a haemolymph paederine is released which acts as an irritant and this leads to dermatitis 

Paederus dermatitis is very common in India and there are many regions where it is endemic The City of Kangra in Himachal is located in a valley. It becomes hot and humid in monsoons with temperatures up to 40⁰C and lots of rain. This makes Kangra an ideal breeding ground for Peaderus beetle, which further results in many cases of Paedrus dermatitis here.

This a case report of one such case with an interesting finding of a kissing lesion on the forearm.

Case Report

A 32-year-old male presented in the Skin OPD. He had two well-defined erythematous plaques with a central cyanotic hue, and vehicles on his right elbow crease on the flexor aspect (Figure 1). The patient had an associated burning sensation at the site of the lesion. The patient slept on the floor the night before and noticed a burning sensation and the lesions immediately after waking up in the morning. The lesions were typical of kissing lesions of Paederus dermatitis which occurs because of the transfer of the irritant from one area to the adjacent areas of skin [1]. The diagnosis of paederus dermatitis was made. The patient was treated with topical mometasone and fusidic acid. The lesions resolved in two weeks without residual pigmentation. 

Figure 1: Erythematous Annular Skin Lesions with Central Crusting on the Forearm

Lesions associated with PD are clinically similar to herpes zoster and phytophotodermatitis rather than an insect bite reaction. They have a linear configuration on the exposed area of the body and heal with hyperpigmentation in two weeks [4]. It is a self-limiting disorder and is usually characterized by the sudden appearance of vesiculobullous lesions on an erythematous base, with a burning, stinging sensation on exposed areas in hot and humid climates. Paederus beetles do not bite or sting but when beetles are accidentally crushed on the human body or people try to remove the beetle, coelomic fluid containing the potent vesicant paederine is released from the beetle, and causes vesicant lesions on the skin [4].

However, macular form of hyperpigmentation is a common sequela that can last up to a month. Extensive exfoliation and ulceration may occur also. Apart from kissing lesions, there can be other common morphological variants like dermatitis linearis or localized pustular dermatitis. Passive transfer of toxin to the genitals through fingers can also happen, producing lesions there. Just like that ocular involvement can similarly occur, which may present as keratoconjunctivitis or periorbital dermatitis popularly known as “Nairobi Eye.” The lesions are usually noticed on waking up in the morning because of the nocturnal nature of the insects, thus acquiring names such as “night burn “or “wake and see” disease [5].

Treatment of paederus dermatitis initially involves removing the irritant by washing the area with soap and water, followed by the application of topical steroids [3].

Diagnosis is usually made on the basis of the history given by the patient and the findings of clinical examination. PD can easily be diagnosed by vesiculopustular lesions on an erythematous background, with a sudden burning and stinging sensation. Hot climatic conditions, an increase in the number of similar cases, and the presence of whiplash linear lesions, kissing lesions, or drip marks support the diagnosis [6]. Cases with atypical clinical findings, such as severe necrosis, diffuse erythema, and desquamation, have also been reported, though none of them were seen in this case [7]. In severe cases, PD can cause symptoms like neuralgia, arthralgia, fever, and vomiting [8].

Although PD is a self-limiting disorder, the sudden appearance of lesions may cause distress Patients usually do not have enough information about the cause of the overnight burning lesions. patients often think they have burnt their skin at night and most patients do not recollect seeing the beetle either. Informing the public about PD and teaching about taking preventive measures can decrease the incidence. Ventilation panes, open windows, and doors facilitate the entry of rove beetles into houses as the beetle gets attracted to the light source, so simple things like closing the doors and the windows before turning on the lights, covering the doors and the windows with an insect-proof mesh and sleeping indoors will prevent the entry of insects and avoid contact with the beetle. The use of insecticide spray will also help decrease the beetle population. In addition, patients must be informed not to crush the beetles or forcefully remove them from their skin and not to scratch primary lesions. They should also be advised to wash the affected skin with soap and water to decrease the effects of paederine.

1. Vijayasankar, P. et al. “Kissing lesions in Paederus dermatitis.” The American Journal of Tropical Medicine and Hygiene, vol. 101, no. 1, 2019, pp. 5–5.

2. Mammino, J.J. “Paederus dermatitis: an outbreak on a medical mission boat in the Amazon.” The Journal of Clinical and Aesthetic Dermatology, vol. 4, no. 1, 2011, pp. 44–46.

3. Singh, G. and Ali, S.Y. “Paederus dermatitis.” Indian Journal of Dermatology, Venereology and Leprology, vol. 73, no. 1, 2007, pp. 13–15.

4. Sendur, N. et al. “Paederus dermatitis: a report of 46 cases in Aydin, Turkey.” Dermatology, vol. 199, no. 4, 1999, pp. 353–355.

5. Karthikeyan, K. and Kumar, A. “Paederus dermatitis.” Indian Journal of Dermatology, Venereology and Leprology, vol. 83, no. 4, 2017, pp. 424–431.

6. Uslular, C. et al. “An epidemicity of Paederus species in Cukurova region.” Cutis, vol. 69, no. 4, 2002, pp. 277–279.

7. Vanhecke, C. et al. “Paederus dermatitis: a retrospective study of 74 cases occurring in 2008 in Guinea Conakry.” Annales de Dermatologie et de Vénéréologie, vol. 137, no. 3, 2010, pp. 189–193.

8. Kamaladasa, S.D. et al. “An outbreak of Paederus dermatitis in a suburban hospital in Sri Lanka.” International Journal of Dermatology, vol. 36, no. 1, 1997, pp. 34–36.