This is a localized skin reaction to a substance in the environment that causes the skin to become red and itchy, according to the National Eczema Association. Often the skin immediately reacts to irritants, such as chemicals (acids, cleaning agents, soaps), abrasion, or heat, and is thus known as irritant contact eczema. Other times, the skin reacts slowly (about 48 to 96 hours) after contact with a substance that the immune system recognizes as foreign or that you’ve become allergic to, such as poison ivy, nickel, or latex — this is called allergic contact eczema, notes the Mayo Clinic.