Ouch. For some users of tooth whiteners, seeking whiter teeth could become a painful pursuit.

RODALE NEWS, EMMAUS, PA—A day of orange juice, coffee, and red wine can leave your pearly whites less pearly than you’d like. But if you bed down with a tray full of whitening gel in your mouth, you could wake up with slightly less enamel on your teeth—and perhaps some pain, too. A new study published this month in the Journal of Dentistry finds that our pursuit of perfectly colored incisors may cause the tough outer layer of our teeth to wear thin, possibly leading to tooth sensitivity, irritation, and decay.

THE DETAILS: Researchers tested five major brands of over-the-counter tooth whiteners (some strips, others in tray form) that contained either hydrogen peroxide or carbamide peroxide as bleaching agents: Crest Whitestrips Premium Plus, Crest Whitestrips Supreme, Nite White ACP, Rembrandt, and Opalescence Treswhite. The products were applied to 65 human tooth samples in keeping with the manufacturers’ instructions. In all cases, there was some loss of enamel at the scale of nanometers, or billionths of a meter, with the biggest reduction seen with the Opalescense Treswhite trays.

WHAT IT MEANS: It’s a yellow light for seeking whiter teeth: proceed with caution. Weakened enamel can lead to tooth sensitivity, pain, gum irritation, and, in rare cases, tooth decay. But that doesn’t mean giving up on tooth whiteners, says study author Shereen Azer, BDS, MSc, MS, assistant professor in the Division of Restorative and Prosthetic Dentistry at Ohio State University’s College of Dentistry. “People just have to understand that tooth whitening is not without side effects,” he says. The enamel loss seen in the study probably wouldn’t be problematic for most people, Dr. Azer says, unless their enamel was weakened to begin with.

Whether your teeth are already too sensitive, or you’re worried about side effects from whitening, here are a few ways to beef up your tooth enamel:

• Visit your dentist regularly. Getting a professional cleaning every six months helps cut down on the need for whitening products in the first place.

• Drink your milk. Weak enamel is actually a result of lost calcium, Azer says, but your body has a natural ability to repair it. “That loss of calcium is regained after a while from your saliva,” he says. You can help things along by taking calcium supplements or getting more calcium from dietary sources, like milk, fortified cereals, canned salmon, and collard greens.

• Buy better toothpastes. Enamel-building calcium comes in remineralizing toothpastes and fluoride gels, says Azer, which are in the dental health aisle alongside those whitening strips. And if you experience irritation from whitening products, look for toothpastes free of sodium laurel sulfates, which can further irritate gums.

• Replace your brush. “Some toothbrushes, if not used correctly, can weaken enamel,” Azer says. Have your dentist show you the best way to brush your teeth. Or invest in an electric brush, which Azer says are “excellent, much better than hand brushes.” If you prefer the manual kind, he suggests buying soft bristles instead of hard.