Allergy to shellfish (molluscs and crustaceans): shrimps, lobster, scampi, mussels, whose chemical composition is based on tropomyosin (T).There is no standard cross reactivity between P and T. However, shellfish T has a homology with that of invertebrates such as arachnids and cockroaches, so that positive skin reactions to shellfish can be found in religiously abstinent subjects like orthodox Je