Key Takeaways Sleeping with a fan on at night is generally safe and may improve sleep by keeping the bedroom cool, providing white noise, and improving air circulation. Fans can worsen allergies, asthma, dry eyes, or sinus irritation if they blow dust, allergens, or dry air directly at your face. Sleeping with a fan on all night is not inherently bad for your health, and, for many people, it can make sleep more comfortable.