These welts might result from skin irritations, allergies, or even some skin disorders such as eczema. To help them disappear, you could get an over-the-counter hydrocortisone cream. This cream will reduce the swelling. Avoid itching or scratching to prevent further irritation. Also, remember to clean the affected area and keep it dry. But if these rashes are still there after doing all these things then go see a dermatologist.