This is what sleeping with a fan on all night does to your body

It feels good, but is it good for you? (Picture: Getty Images) As the mercury tips 35°C in parts of the country this week, those of us without the luxury of aircon are clinging to our fans for respite. For many, the only way to get a decent night’s sleep is to leave one whirring away by the bed until morning in the hope of getting a decent night’s sleep. But while a fan can make your sweltering bedroom feel far more bearable, experts say sleeping with it on isn’t without its downsides. From triggering allergies to drying out your skin, here’s what this overnight airflow does to your body – and whether your heatwave saviour actually does you more harm than good come bedtime. Allergies and asthma Dr Hana Patel, NHS GP and resident sleep expert at Time4Sleep, tells Metro: ‘Those who experience allergies, especially allergies to dust or hayfever, may find that their symptoms are agitated by sleeping with a fan. Ask Metro Use AI to go deeper into the stories you care about – powered by Metro and trusted publications. ‘This is because the fan will circulate allergens around the room, increasing the likelihood of them being breathed in, or coming into contact with your skin.’ The most obvious sign of this is waking up after a night of sleeping by the fan with symptoms like a sore throat, itching or sneezing. Fans circulate dust mites, spores and pollen around a room (Picture: Getty Images) Similarly, the way this appliance can stir up any dust mites, spores or pollen in your room can also make asthma worse — in which case, Dr Patel says ‘it may be a good idea to avoid sleeping with a fan.’ ‘You are likely to find that the fan will cause more issues than benefits, due to it inflaming your medical condition,’ she says. ‘This is especially the case for children.’ Congestion Waking up feeling bunged up as if you have a winter cold, despite the summer climes? According to sleep therapist Natalie Pennicotte-Collier, that’s likely down to your trusty cooling device as well. The resident sleep expert at MattressNextDay tells Metro: ‘A fan running all night progressively dries the mucosal membranes lining your nose, throat and upper airways. Your body responds by producing more mucus. Do you think sleeping with a fan on all night is worth it during a heatwave? Absolutely, the comfort outweighs the negatives.Check Yes, but only as a last resort.Check No, it's better to find alternative cooling methods.Check Sign up to Metro's The Slice newsletter for your guide to what's on in London, with trusted reviews, offers and giveaways. Muscle pain ‘If the fan is close to you, you may also find that the consistent cold air leads to your muscles tightening as you sleep, causing you to feel aches when you wake up,’ explains Dr Patel. As well as cramping and pain, pre-existing issues may also be exacerbated. Dry eyes, mouth and skin When it comes to skin, Dr Patel likens the effect of sleeping with a fan on to those of a long-haul flight, advising: ‘The key is to moisturise before and after bed to prevent irritation.’ According to Tina Patel, contact lens optician at Feel Good Contacts, eyes can feel dry, gritty or irritated too, ‘especially if it’s blowing directly towards your face.’ The cold air dries out your airways (Picture: Getty Images) ‘This effect is often worse in already warm, dry environments, or for those with sensitive eyes,’ she continues. ‘For contact lens wearers who experience dry or irritated eyes, applying eye drops and switching to glasses in the evening may help reduce irritation overnight.’ As a result of all this, your sleep can then end up suffering, with Natalie warning: ‘Many of the clients who come to me struggling with early morning waking, convinced it is stress or anxiety, are actually experiencing the overnight effect of airway dryness from fan exposure.’ How to reduce the negative impact of your fan If you just can’t break your nighttime fan habit, there are some ways to mitigate its effects on your health: Put the fan in the hallway with bedroom doors open. Dr Patel says: ‘This allows the air to circulate between rooms without many of the negative effects of having a fan in the same room.’ Use your fan to cool the room before sleep, or set a timer so it switches off after an hour. Point the fan towards the ceiling or a wall, not directly at your face or body, to reduce airway drying while still cooling the room. Wipe down the fan blades prior to use to reduce the amount of dust circulated. Additionally, regularly vacuum and dust your bedroom so there’s less dust to circulate. Natalie says: ‘Stay well hydrated through the day and keep water by your bed. Counteracting the drying effect of fan use starts with good hydration.’ Consider other methods to cool down if issues persist, such as temperature-regulating mattress toppers and breathable bedsheets. 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