Paederus contact dermatitis is a skin disease caused by beetles of the genus Paederus and the release of a vesicant substance called paederin. It is worldwide distributed; However, it is more common in rainy seasons and hot climates. The clinical manifestations are vesicle-pustules that settle on erythematous skin. Treatment is based on washing with soap and water to neutralize the action of the toxin and the administration of topical steroids in short cycles. We report the case of a 28-year-old male patient who came to the dermatology clinic with a 48-hour history of two erythematous plaques with central blisters plus superficial ulceration located on the flexor aspect of the arm and right forearm, accompanied by a sensation of burning and itching at the site of the lesions, without other accompanying symptoms. As background, he states that he was on vacation in the coastal region of Ecuador when the lesions appeared. An incisional biopsy was performed and due to the clinical characteristics and the history of travel to a tropical region, it was diagnosed as Paederus dermatitis and treatment with antihistamines, topical steroids and cold compresses was indicated. After 8 days of treatment, the lesions subsided, leaving post-inflammatory hyperpigmentation.