What is the most likely cause of redness and itching on the sole of a foot after exposure in the Caribbean?

The symptoms of redness and itching on the sole of the foot, especially after exposure in a tropical area like the Caribbean, are highly suggestive of a hookworm infection. Hookworms, which include species such as Ancylostoma duodenale and Necator americanus, are transmitted through larvae that penetrate the skin, often when walking barefoot on contaminated soil or areas where infected feces are present.

When hookworm larvae come into contact with the skin, they cause a localized inflammatory response that presents as redness and itching. This reaction is sometimes referred to as "ground itch." The geographic context of the Caribbean further supports this conclusion, as hookworm infections are common in regions with warm climates and poor sanitation.

While other conditions such as scabies, fungal infections, and insect bites can also cause similar symptoms, they are less likely given the exposure history. Scabies typically requires close personal contact for transmission and may present with additional symptoms like burrows or papules. Fungal infections would generally have a characteristic scaling appearance, and insect bites might cause localized lesions but usually would not manifest solely as itching and redness without a more significant reaction. Thus, the context of the Caribbean exposure and the specific symptoms strongly favor hookworm as the likely cause.