When the temperatures start to rise, many of us won't think twice about putting a fan on to cool down the room before trying to drift off, but those with allergies - including hay fever - might want to reconsider.
Mark Reddick, who is known as The Sleep Advisor, told The Sun that sleeping with a fan can cause a couple of problems.
A fan works by moving cool, dry air around the room, which is ideal if you're feeling too warm, but it can also dry out your throat, nose and eyes, which is less than ideal if you're already dealing with those issues because of hay fever.
As well as circulating air, fans can also circulate pollen particles and dust that's lying around in your room, or even caught on the fan's blades - not good.
Mark told the newspaper: "For some people, having a ceiling or floor fan in the room helps them fall asleep and stay cool during the night.
"For others, it can keep them awake, trigger asthma attacks or dry out their eyes."
He added: "As a fan moves air around the room, it causes flurries of dust and pollen to make their way into your sinuses.
"If you're prone to allergies, asthma, and hay fever, this could stir up a whole lot of trouble."
With temperatures set to top 30C in parts of the UK this week, the Met Office has also warned that pollen levels will be high.
You can help reduce the amount of pollen that gets inside your bedroom by keeping windows shut at night and in the morning, when it might drift through on a breeze.
You can combat the heat without a fan by popping your pillow case and bed sheet in the freezer before taking them to bed with you, or by chucking some icy cold water into a
hot water bottle.
Last month saw the introduction of a £1 hay fever product which has been described as a 'life saver'.
Budget shop Savers is selling hay fever relief wipes, which are made by Nuage.
The reviews are all fairly glowing, with one person writing: "Bought these for my daughter when horse riding as she tends to get itchy eyes... perfect."
A second said: "These are a life saver for my little girl! She struggles so bad and these have made such a difference to her!"