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Imagine yourself frolicking on a warm, sandy beach on a sunny summer day. At mid day, when the sun is at it's hottest, you decide to take a dip in the calm lake water. Unsuspectingly, you enter the water, and it is not long before you encounter this!


courtesy of Center for Disease Control

You actually will not be able to see this, but in waters infested with schistosome cercaria, these creatures will surely approach you. Ideally, they would like to encounter birds or other mammals, but every so often humans cross their paths. If these creatures are so small and puny, why should we be concerned? Although the initial encounter will surely go unnoticed, in a few hours to days, you will be left with an umpleasant reminder of their presence: a nasty, itch rash called cercarial dermatitis, commonly known as "swimmer's itch."
This webpage is my attempt to provide a comprehensive overview of the condition cercarial dermatitis as well as the organism that causes it, so click away and enjoy!


The common name for cercariae dermatitis is swimmer's itch, which describes one of the most common ways humans encounter this condition. Other names include "clam digger's itch", "diver's itch", or other variations on the itch theme. Originally it was described as schistosome dermatitis by Cort in 1928; however, in 1930, Vogel used the term cercarial dermatitis, which is the name used to this day. In Japan, it was known as karube or konganbyo if it was more severe.

History of Discovery

The earliest description that I could trace back in the literature was a reference to an 1855 description by LaValette of the erythemous maculo-papular eruption that is presumed to have been cercarial dermatitis. In Japan, karube, a maculo-papular rash, was common among rice farmers that spent lots of time in cercariae-infested water. At the turn of the century, it was assumed that human schistosomiasis S. japonicum was the cause of this rash. However, in 1913, Miyagawa began to cast doubt on this presupposition. In the American scientific literature, Cort was the first to demonstrate that swimmer's itch was caused by the cercariae of non-human schistosomiasis in 1928. Prior to that, it was believed that all such eruptions were caused by human schistosomiasis.

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