Yes. It's fine for most people, though it can dry out your nose, throat, or skin if the airflow hits you directly all night.
Fans are one of the most common sleep aids around, mostly for the steady background noise and the airflow that makes a room feel less stuffy. Millions of people run one every night without any issue.
The concerns that come up — dry sinuses, sore throat, aggravated allergies — are real for some people, but they come from positioning and dust, not from the fan itself being dangerous.
Moving air helps sweat evaporate, which makes a room feel a few degrees cooler even though the fan doesn't actually lower the temperature. The white noise also masks street sounds, snoring, or a partner's movement, which helps some people fall asleep faster.
Angle the fan away from your face and toward the wall or ceiling so it circulates air without blasting you directly. Clean the blades and grille every month or two — a dusty fan is the main reason people wake up congested.
A fan does not lower the room's actual air temperature; it only moves air around. On genuinely hot nights, pair it with an open window, a cooler part of the house, or air conditioning for real temperature drops.
A fan running overnight is safe for nearly everyone and genuinely helps a lot of people sleep better. Just keep it clean and angled away from direct contact with your face if you tend to wake up dry.
Cold or overly cooled muscles from direct, sustained airflow can feel stiff for some people, though it's not injury, just discomfort. Angling the fan away from your neck and shoulders usually fixes it.
It can, if the fan itself is dusty or it's stirring up dust and pollen already in the room. Regular cleaning and closed windows during high-pollen periods reduce the effect.
Yes, temperature doesn't make it unsafe. In colder months some people prefer it off simply because they don't need the cooling effect, not for any safety reason.
A typical box or tower fan uses about 40-100 watts, roughly the same as a couple of LED bulbs, so running one all night costs only a few cents.