There are many types of rashes, including those caused by toxins (such as poison ivy) or illnesses (such as roseola or chicken pox). If you get a red, itchy rash with no known cause, it could be allergic contact dermatitis.
This itchy skin rash can result from exposure to a chemical or compound that causes a response from the skin’s immune system. The rash will arise at the point of contact with the allergen. The area is usually a pink or red color and feels itchy. Contact dermatitis may appear flat or raised, and in severe cases, blisters filled with clear fluid may result.
Although some people react more quickly than others, these rashes tend to take time to develop and don't occur with the first exposure. “Allergic contact dermatitis is something that's what we call a delayed type hypersensitivity,” says Keith Choate, MD, PhD, a Yale Medicine dermatologist. “Someone will be, for example, exposed in the garden on Sunday, and then start noticing that they have an eruption on Monday. So it's not instantaneous. It takes time.”
Yale Medicine dermatologists have highly specialized expertise in treating complex skin disorders, including skin testing to determine the specific cause of a person's allergic contact dermatitis. "Our physicians are really dedicated to getting answers," Dr. Choate says.