Polyurethane (PU) products are a versatile group of polymers formed by reacting a di- or polyfunctional isocyanate with hydroxyl-group-containing compounds such as polyols or polyesters, in the presence of suitable catalysts and additives. The isocyanate raw materials of PU are a relatively important cause of occupational allergic contact dermatitis. Occupational allergic contact dermatitis is most commonly induced by diphenylmethane diisocyanate (MDI)-based products. Ingredients of PU resins may also irritate the skin. Isocyanate-induced contact urticaria is a very rare disease, although Ige-mediated sensitization to isocyanates is possible. It is advisable to test polyurethane-exposed patients with their own isocyanate-containing materials from work in addition to the commercially available patch-test preparations of diisocyanates. Additional test reading on day 7 is recommended since positive reactions may appear late. MDA is an important marker of MDI sensitivity.