Hot water bottles keep you toasty, ease aches and pains and more. So why don't more Americans use them?

When little aches strike, it’s understandable to reach for the closest over-the-counter pain reliever and hope for the best. But doctors say the solution to what ails you could be as simple as turning on your tap.

While they're not used as commonly in America, hot water bottles — rubber containers that act as a sort of warm compress — are a must-have household item in some parts of Europe, where central heating is less common. That infatuation shows no sign of slowing down: In 2022, U.K. retailers reported record sales of hot water bottles during a cold snap. TikTok is also filled with testimonials from people who love their hot water bottles.

At baseline, a hot water bottle can help keep you warm. But doctors say there’s so much more to this simple device than that. “One of the biggest benefits of using a hot water bottle is that it’s inexpensive, easy to find and simple to use,” Dr. Caitlyn Mooney, assistant professor in the Division of Sports Medicine at Vanderbilt University Medical Center, tells Yahoo Life. “It’s also helpful for people who cannot take pain medications.”

So, what can a hot water bottle do — and how do you actually use one? Doctors explain.

It may help ease stiffness

Mooney lists off easing joint stiffness as a big perk of using a hot water bottle. The Arthritis Foundation cites heat therapy — which includes hot water bottles, heating pads and steam towels — as "one of the oldest, cheapest and safest forms of complementary therapy."

Research shows that heat therapy can help muscles relax and improve blood circulation, easing stiffness in the process. When you heat up a sore joint, your blood vessels get bigger, the Arthritis Foundation explains. This allows more blood, oxygen and nutrients to be delivered to those areas and helps them to relax. As such, heat therapy is often also recommended for lower back and neck pain.

It can make stretching easier

Hot water bottles don’t just ease stiff joints — they can also soothe achy muscles, Mooney says. “Some people also use heat to help warm up or stretch muscles before exercising to prevent injuries,” she says.

It’s not entirely clear why heat therapy can help with muscles, but Mooney says it’s likely similar to the effect seen with joints — meaning, the heat can promote good blood circulation and deliver important nutrients to muscles. Research shows that applying heat before you stretch can also help improve flexibility and range of motion, while the heat can help stretch out collagen, which helps with muscle growth and repair.

It can help with period cramps

The American College of Obstetricians and Gynecologists (ACOG) specifically recommends using a hot water bottle on your abdomen or lower back to help with period cramps. “The thought process is that the muscles can relax, which may help with the pain because the warmth helps increase blood circulation,” Dr. Christine Greves, an ob-gyn at the Winnie Palmer Hospital for Women and Babies, tells Yahoo Life.

A hot water bottle can also be helpful for back pain during pregnancy, according to ACOG. The organization just recommends wrapping the bottle in a towel to avoid overheating.

It can warm you up

While a hot water bottle has a range of uses for your muscles and joints, it can also simply help you to stay warm when temperatures drop, Mooney points out. You can try putting a hot water bottle between the sheets before you get into bed at night, or just keeping it on you during the daytime. Again, this is much more common in Europe, where people will use hot water bottles to save on heating costs while still staying warm.

How to use a hot water bottle

Using a hot water bottle is relatively simple: You just unscrew the top, fill it with hot water from the tap, screw the cap back on and apply it to an area of your body that needs it. But there are some risks to keep in mind too.

“The biggest danger is burns,” Mooney says. “Hot water bottles can leak or even burst, spilling hot water.” Also, if the water you put into the bottle is too hot, the bottle can also overheat and burn your skin, she points out. (For this reason, some people buy hot water bottle covers to provide a protective barrier — and cozy comfort item.

“To stay safe, always check the temperature of the hot water bottle before using it,” Mooney says. “Make sure it’s not too hot to touch.” And check the seal to make sure no hot water is leaking out.

Heat should only be applied for about 15 minutes before taking a break, Greves notes. “You should remove it immediately if it causes any discomfort or if you notice redness or irritation on your skin,” adds Mooney. “It is also recommended that heat not be used on new injuries that are still swollen or inflamed.”