Allergic skin reactions on the legs may occur due to contact with allergens, insect bites, irritants, or other triggers. To relieve symptoms, apply a mild topical corticosteroid cream (such as hydrocortisone) and take a non-drowsy oral antihistamine (such as cetirizine) to reduce itching and inflammation. Identify and avoid potential triggers, and avoid scratching, using harsh soaps or detergents, or wearing tight clothing. If the rash spreads, becomes painful, or does not improve within a few days, consult a dermatologist for proper diagnosis and treatment.