How does the onset of Swimmer's Itch differ from the immediate osmotic sting?

The noticeable rash associated with Swimmer's Itch typically appears minutes or up to two days after leaving the water.

Swimmer's Itch, also known as cercarial dermatitis, is fundamentally different from the instantaneous osmotic sting because it is an allergic reaction triggered by microscopic fluke larvae, not the salt concentration itself. While there might be a slight initial tingling upon initial contact as the parasite burrows, the defining characteristic of Swimmer's Itch is its delayed manifestation. The small, reddish pimples or blisters that constitute the rash do not appear right away; instead, they usually develop sometime between a few minutes and as long as two days following exposure. This contrasts sharply with the osmotic sting, which is an immediate physical sensation tied directly to the moment the skin encounters the hypertonic saltwater environment.