We all want a gleaming, bright smile, but is whitening your teeth a safe option?

While it can be safe, there are key differences between whitening your teeth at home versus at a dentist’s office, host Dr. Saleyha Ahsan explains in BritLab’s video below. BritLab is a channel created by BBC Worldwide.

Read: 5 Ways To Get Whiter Teeth In A Natural, Healthy Way

The effectiveness of teeth whitening comes down to one ingredient: hydrogen peroxide. The more of it there is, the whiter your teeth will be; however, more isn’t always a good thing. In fact, too much hydrogen peroxide in a product is not only illegal, it can also burn your gums, mouth, and ruin your tooth enamel.

The maximum amount of hydrogen peroxide in a whitening gel is 6 percent, according to a law set forth by the European Union. These products can only be sold to dental professionals.

If you’d rather a cheaper option, you can buy at-home whitening kits. Although still effective, over-the-counter kits can only legally contain 0.1 percent hydrogen peroxide.

In the video, Ahsan demonstrates the effectiveness of 0.1 percent vs. 6 percent vs. 35 percent, which some products illegally sold online contain.

For the whitest teeth and safest option, you should let a professional do the job. But the cheapest option is to prevent discoloration in the first place. Although factors like aging are uncontrollable, you can choose what you eat and if you smoke. Some food and drink that contribute to discoloration are berries, red wine, coffee, tea, and soft drinks.

See also: Pearly Whites: 6 Ways On How To Whiten Teeth Without Seeing A Dentist

Which OTC Teeth Whitening Solution Is Best, And Are Any Of Them Truly Safe?