Consuming hot or spicy foods causes some people to sweat while eating in order to lower their body temperature, according to HowStuffWorks. Medical problems, including Parkinson's disease, certain viruses, and nerve damage related to diabetes or surgery, can also cause people to sweat while eating.
Gustatory hyperhidrosis, or gustatory sweating, is the medical term that refers to sweating while eating, according to HowStuffWorks. Gustatory sweating usually involves areas around the mouth, scalp and neck. Depending on the trigger for gustatory sweating, it may occur on one or both sides of the face. It's an involuntary reaction, meaning that the person is unable to control it.
Because sweating is controlled by the sympathetic nervous system, problems with this system sometimes lead to gustatory sweating, according to HowStuffWorks. Uncontrolled high blood sugar levels in diabetics can lead to nerve damage over time, which commonly leads to gustatory sweating. Frey's syndrome, a condition in which nerve endings near the parotid glands are damaged during surgery, is another common reason for gustatory sweating. In either case, the nerve damage causes a sweat nerve to be mistaken for a salivary nerve. Thus, when the brain signals the body to produce saliva while eating, it produces sweat instead.