It might seem harmless or even comforting, but sleeping with a fan running all night could actually be doing more harm than good. Experts warn that while it helps with airflow and cooling, it can also circulate dust, pollen, and allergens directly into your nose and mouth while you sleep.

If you suffer from allergies, asthma, or sinus problems, this can make things worse — causing dry eyes, headaches, and congestion by morning. Even healthy sleepers can wake up with sore throats or muscle stiffness from prolonged cold air exposure.

To stay safe, try setting a timer for the fan to turn off after you fall asleep, or clean it regularly to prevent dust buildup. Sleeping cool is fine — just make sure your air isn’t working against your health.