Dermatitis caused by algae and bryozoans

Algae and Bryozoans can cause various clinical pictures. Algae are found in all aquatic environments. Some species of Cyanophyceae (“blue-green algae”) and Dinophyceae classes, present in salt and freshwater, produce one or more toxins, some of which are strongly neurotoxic or hepatotoxic, while others provoke gastroenteritis and skin disorders. The skin toxicity can manifest in humans with irritant and allergic reactions. A particular alga of the Cyanophyceae, present in various localities of Australia, Florida and Hawaii, periodically induces the so-called swimmer’s itch, a dermatitis whose onset occurs a few minutes after bathing, with intense itching and burning sensations, followed after 3-8 h by blisters leaving painful erosions in the areas covered by the swimming costume. Skin protothecosis is another infection induced by seaweed, that mainly affects immunocompromised subjects, triggering various clinical pictures. The affliction, reported in various parts of the world, is difficult to diagnose. The lesions can persist for years and there is no known elective treatment. Bryozoans (moss), belonging to the animal kingdom, can cause quite a disabling contact dermatitis in fishermen, featuring dry, fissuring and exudative lesions of the hands and forearms. The complaint, that may also be of an allergic nature, can become generalized.