Allergic Contact DermatitisThe classic of this is reaction to poison ivy. If you take a walk in the woods, brush against a plant, and note the appearance of blisters on the skin two days later, the diagnosis of allergic contact reaction to poison ivy is obvious. However, reactions to poison ivy or poison oak may be atypical and may be very subtle.
There are many chemicals in our environment which can cause allergic contact dermatitis. Examples would be nickel, fragrances, preservatives, rubber, or latex products. The hallmark of allergic contact dermatitis is that only some people exposed to the allergen will develop a dermatitis. It is not universal. If a rash which appears to be allergic contact eczema appears, a careful history and physical may be all that is required to uncover the culprit; however, in some cases more extensive usage testing or patch testing may be needed.