Urocanic acid is a major chemoattractant for the skin-penetrating parasitic nematode Strongyloides stercoralis

Safer D, Brenes M, Dunipace S and G Schad. (2007) Proc. Natl. Acad. USA 102:1627-1630.
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More than 600 million people worldwide are infected with skin-penetrating parasites that contribute to ill health and poor physical and cognitive development. Now, Penn researchers from the School of Medicine and School of Veterinary Medicine have found a link between some of these disease-causing parasites and a chemical secreted from skin.

Urocanic acid, which is found in mammalian skin, attracts the parasite known as Strongyloides stercoralis. Metal ions, the scientists found, can lessen the level of attraction between the parasites and the urocanic acid, potentially offering a new way to prevent nematode infection. The research suggests that topical application of calcium, magnesium or manganese creams could diminish the lure to parasites and greatly reduce the risk of disease to people in developing nations across the world.