Unless you live somewhere that’s moderate year round, chances are you’ve relied on a air cooling fan to make an otherwise steamy room more bearable. While fans don’t always add cold air to the mix, they help circulate the air so that our bodies can better cool down. In some cases, though, air conditioning is a much better option. “If a person has allergies, asthma, or eczema that are exacerbated by pollen, then it's best to use air conditioners, which filter out pollen and allow the windows to be closed,” says Hadley King, M.D., NYC-based dermatologist and clinical instructor of dermatology at the Weill Medical College of Cornell University. But the reality is that air conditioning isn’t always available—and in some cases, skin conditions like eczema can be triggered by heat. In these situations, a cooling fan can be helpful, says Hadley, as long as it’s used correctly.

If you’re using a fan, Hadley suggests positioning it so that it's not blowing directly on you. “Air blowing over the skin can contribute to drying it out,” she explains. If you are allergic to pollen, avoid window fans, which can actually circulate more pollen into the air inside and make matters worse. Finally, be aware that fans are “dust collectors,” says Bruce Prenner, M.D., board-certified allergist at Allergy Associates Medical Group in San Diego, California. While they aren’t generally a source of dust mites (the little buggers prefer burrowing into soft things like blankets, pillows, and curtains) dust itself can still cause sneezing and other reactions in people who are sensitive to allergens. For this reason, it’s important to keep any portable fans clean and dust-free.

Fans don’t need to be fancy to work well, but there are a few other things (in addition to the best practices above) that our experts suggest considering when shopping for a portable fan. For SELF's product reviews, where we rigorously test and evaluate all kinds of wellness products to help you decide what's worth buying, we wanted to know exactly what those criteria were. Here's what the experts suggest, and what we pay attention to when testing cooling fans for reviews.