Hi Welcome to Healthcare Magic Forum Looks like you have developed a lesion of Vector dermatitis, also known as Paederus dermatitis.. Paederus dermatitis is a peculiar, irritant contact dermatitis characterized by a sudden onset of red lesions on exposed areas of the body. The disease is provoked by an insect belonging to the genus Paederus. You need to apply an antibiotic/steroid combination cream over the lesion twice a day. Take oral antihistamine to decrease the swelling. Do not use any moisturizer or oils till the time the lesion heals . If the lesions continue to increase inspite of the above treatment, then you might have to see a dermatologist as in severe cases, short term courses of oral antibiotics or oral steroids may be required. Hope it helps Wishing you speedy recovery Dr Geetika Paul