Many people cannot sleep without using a fan, but scientists say this could be bad for us. This is unwelcome news for those of us struggling to nod off during the current scorching hot weather. According to sleep experts at the website Sleep Advisor, there are many reasons why the use of a fan could be detrimental to our health. Fans can cause problems for people with asthma or hay fever. The rotating blades of fans cause dust and pollen to circulate around the room and add to an asthmatic's sleeplessness. Sleep Advisor says circulating air can dry out and irritate your eyes, mouth and sinuses, which also makes it difficult to sleep. Fans also cool the air and can make muscles tense up and cramp.

Other sleep experts disagree and say there are no dangers to health from using a fan. Dr Len Horovitz, a specialist on the health of the respiratory system, said: "There's nothing about a fan that's toxic. There's nothing wrong with circulating air." He told the Live Science website that if a fan stops us sweating, it will help us to sleep. He said people should keep fans at a safe distance from their bed and not have them blowing directly at their body. He also recommended keeping an air filter in the bedroom to reduce the levels of dust in the room. Sleeping with a fan may be preferable to using an air conditioner, which can chill any sweat on our body and possibly cause us to wake up with a cold.