Eruption of transient oedematous swellings of the dermis or subcutaneous tissues as a result of skin exposure to certain contactants. Erythema associated with itching, wheals at the precise site of contact and generalized urticaria with anaphylactoid symptoms may occur. The mechanisms may be either of an immunological (IgE-mediated) nature, e.g. following exposure to nickel, cosmetics and fish, or non-immunological. Examples to the latter include skin contact to nettles and jellyfish.