Why does eating spicy food sometimes make a person sweat?

Spicy foods, such as jalapenos and chili peppers, contain a chemical which stimulates the same nerve endings in the mouth as does a rise in temperature. These nerves, which don't know the difference, send messages to the brain telling it the temperature near your face has increased. Your brain reacts by activating cooling mechanisms to reduce the temperature around your face, and one of those mechanisms is perspiration.