When used correctly, OTC oral care products with small amounts of hydrogen peroxide are safe and effective. Higher percentages of hydrogen peroxide in treatments are safe when applied by a dental professional.
Check with your dental professional before making your own concoctions. Although hydrogen peroxide is affordable and easily accessible (you might already have a bottle at home), maintaining a safe concentration of hydrogen peroxide when mixing at home can be difficult. Also, the mix could overflow if you use a mouthguard that isn't custom-made to fit your mouth, which could irritate your gums. If you have recessed gums, it could even touch an exposed tooth root, causing more sensitivity.
While you'll likely be fine if you swallow a bit of hydrogen peroxide, you should be careful to avoid ingestion. According to the National Capital Poison Center, swallowing some could cause vomiting and stomach aches. Larger amounts could cause stomach bleeding, breathing problems, and even be life-threatening. A dental professional will advise you on what products you can use and how to safely use them for your specific needs.
Whether you're looking for healthier gums or a whiter, more confident smile, hydrogen peroxide is an ingredient that can help you reach your oral health goals. You may already be using hydrogen peroxide in some OTC products and receiving treatment with it at your dental professional's office.
When it comes to DIY mixtures at home, speak with your dental professional about what's safe for your oral health. They'll be able to ensure you're doing what's best to maintain a healthy smile.