Health advisory warns against sudden cooling after sun exposure

Dr. Nguyen Huy Hoang of the Vietnam Underwater and Hyperbaric Medicine Association warns that standing directly in front of strong fans or entering cold air-conditioned rooms immediately after being in the sun can be harmful.

When the body is exposed to heat, blood vessels dilate and sweat production increases, leading to a loss of water and electrolytes. Sudden cooling can cause rapid vasoconstriction and abrupt changes in blood pressure. This poses significant risks to the elderly and individuals with underlying conditions such as hypertension, atherosclerosis, or cardiovascular disease.

Such sudden temperature shifts are linked to circulatory disorders and peripheral facial nerve palsy (seventh cranial nerve paralysis), which may manifest as facial drooping or difficulty closing an eye. Dr. Hoang advises resting in a cool area for 20–30 minutes, drying sweat, and hydrating before using fans or air conditioning. He also recommends using the oscillation setting on fans to avoid direct airflow to the head, face, or neck.