The most likely cause of the illness is a toxin , specifically a seafood neurotoxin such as that seen in ciguatera-type fish poisoning.

Reversal of hot and cold sensations (often called “hot–cold reversal” or “cold allodynia”) is a classic neurologic symptom of certain seafood toxin poisonings, and is strongly associated with ciguatera and related marine toxins rather than with typical bacterial, viral, or parasitic foodborne infections.