Why do I get a headache as soon as I turn on the air conditioner?

　　In general, headaches triggered by exposure to air conditioning may be caused by cold sensitivity, large indoor-outdoor temperature differences, dehydration, migraines, hypertension, and other factors. Symptomatic management through general treatment or medication may be needed. If discomfort occurs, it is recommended to seek timely medical attention and undergo appropriate treatment under a physician's guidance. Detailed explanations are as follows:

　　1. Cold Sensitivity

　　Some individuals are particularly sensitive to cold stimulation. When exposed to cool air from an air conditioner, cerebral blood vessels may rapidly constrict to reduce heat loss. This sudden vasoconstriction may trigger cerebral vasospasm, leading to headaches. It is recommended to avoid direct exposure to cold air from air conditioners or adjust the air conditioner temperature to a suitable range to reduce stimulation to cerebral blood vessels.

　　2. Large Indoor-Outdoor Temperature Differences

　　Significant differences in temperature between indoor and outdoor environments can make it difficult for the body to adapt quickly when entering or exiting air-conditioned rooms. These temperature fluctuations may cause cerebral vasoconstriction and dilation, resulting in headaches, which may be accompanied by symptoms like nasal congestion and runny nose. It is recommended to wear additional clothing when entering air-conditioned rooms or remove layers when leaving to buffer the impact of temperature changes on the body.

　　3. Dehydration

　　Air conditioners reduce indoor humidity, making the air dry. Prolonged exposure to such an environment increases water loss from the body via respiration and skin evaporation, potentially leading to dehydration. Dehydration can affect blood viscosity and circulation, thereby influencing cerebral blood supply and causing headaches, which may be accompanied by symptoms such as thirst, dark urine, and fatigue. It is recommended to replenish fluids regularly and use a humidifier or place a bowl of water indoors to increase air humidity.

　　4. Migraine

　　Temperature fluctuations, dry air, or strong light in air-conditioned environments may act as triggers for migraine attacks. These factors can stimulate sensitive areas in the brain, inducing migraines, which may be accompanied by nausea, vomiting, and sensitivity to light or sound. It is recommended to follow medical advice and use medications such as topiramate tablets, propranolol tablets, or sumatriptan tablets for treatment.

　　5. Hypertension

　　Hypertension refers to persistently elevated arterial blood pressure. Temperature variations in air-conditioned environments may cause blood vessels to constrict and dilate. If hypertension is already present, these changes may lead to blood pressure fluctuations and subsequent headaches, possibly accompanied by dizziness, palpitations, and chest tightness. It is recommended to follow medical instructions and take medications such as nifedipine tablets, methyldopa tablets, or captopril sustained-release tablets to alleviate symptoms.

　　It is recommended to take proper warming measures when using air conditioning, such as preparing long sleeves, trousers, and light jackets to reduce the stimulation of cold air on the blood vessels of the head.