That brown bottle under the bathroom sink has probably been there for years. Many of us grew up watching a parent pour it on a scraped knee and seeing it fizz. Hydrogen peroxide does have some genuinely useful jobs around the house, but one of its most famous uses is now one that doctors tell you to skip.
Key Takeaways
- The 3% hydrogen peroxide sold in drugstores is the only strength meant for home use. Stronger “food grade” (35%) versions can cause serious burns and should never be swallowed or used on the body.
- For cuts and scrapes, plain running water is better. Doctors no longer recommend peroxide for wound cleaning because it can irritate tissue and slow healing.
- For earwax, a few drops can help soften buildup, but skip it if you have a perforated eardrum, ear tubes or signs of an ear infection.
- For teeth whitening, it can lift surface stains, but overuse can cause tooth sensitivity and gum irritation. Check with your dentist first.
- For hair, diluted peroxide can gradually lighten color, but it’s drying, so use it sparingly.
First, know your bottle
Drugstore hydrogen peroxide is a 3% solution, meaning it’s mostly water. At that strength, splashes on the skin usually cause only mild irritation. Hair bleach products typically contain 6% to 10%. So-called “food-grade” hydrogen peroxide is about 35%. Despite the name, it is not food. Poison control experts warn that swallowing it can cause severe internal burns, and in rare cases dangerous gas bubbles in the bloodstream. People have been seriously injured or killed after drinking it as an “alternative therapy.” The FDA has warned against drinking high-strength hydrogen peroxide for medicinal purposes.
Light breaks hydrogen peroxide down into plain water and oxygen, which is why it comes in a dark bottle. If it no longer fizzes when it touches a cut or a sink drain, it has likely lost its strength.
1. Cuts and scrapes: put the bottle down
That satisfying fizz isn’t the germ-killing power many of us assumed. It happens when hydrogen peroxide reacts with an enzyme called catalase, which is found in blood and body tissues. The trouble is that peroxide doesn’t distinguish between bacteria and your own healing cells. Research has shown it can damage fibroblasts, the cells that rebuild skin and connective tissue, and higher concentrations can delay healing.
Mayo Clinic and Cleveland Clinic both advise against using hydrogen peroxide or iodine on cuts. Instead:
- Wash your hands, then press a clean cloth on the wound to stop the bleeding.
- Rinse the wound under clean running water, and wash the skin around it with soap.
- Remove any dirt with clean tweezers.
- Apply a thin layer of antibiotic ointment or petroleum jelly and cover it with a bandage.
See a doctor if the wound is deep or won’t stop bleeding, you can’t get all the dirt out, or you see signs of infection such as spreading redness, warmth, swelling, drainage or worsening pain. You may also need a tetanus shot if it’s been more than five years since your last one and the wound is deep or dirty.
2. Earwax: a gentle softener, with limits
Earwax is normal and protective, and most ears clean themselves. Ear specialists warn against cotton swabs, which can push wax deeper, and ear candles, which can cause burns and don’t work.
If wax does build up and muffle your hearing, a few drops of a softening agent can help. Hydrogen peroxide is one common option, and a related compound, carbamide peroxide, is the active ingredient in many over-the-counter earwax drops. Mineral oil, baby oil and glycerin are other options. To use peroxide:
- Lie on your side with the affected ear facing up.
- Place a few drops of 3% hydrogen peroxide in the ear. Expect some bubbling.
- Stay still for about five minutes, then sit up and let the liquid drain onto a tissue.
Don’t use ear drops if you have a hole in your eardrum, ear tubes, or a history of ear surgery, or if your ear is painful, draining or bleeding. Those symptoms aren’t caused by earwax and need a doctor’s evaluation. If home treatment doesn’t help after a few days, see your doctor, who can safely remove the wax.
3. Teeth whitening: occasional use only
Hydrogen peroxide is the active ingredient in many whitening strips, gels and toothpastes, and it can help lighten surface stains from coffee, tea and red wine. A simple home paste uses 3% peroxide mixed with baking soda:
- Mix about 2 tablespoons of 3% hydrogen peroxide with 1 tablespoon of baking soda to form a paste.
- Brush gently, leave it on for about a minute, then rinse thoroughly. Don’t swallow it.
- Limit this to once a week at most, and less often once you see results.
Freshening mouth rinse: Mix equal parts 3% hydrogen peroxide and water. Swish for about 30 to 60 seconds, then spit it out and rinse with plain water. Never swallow it, and use it only occasionally, since frequent use can irritate the gums.
Overuse can cause tooth sensitivity, irritate your gums and wear down enamel. Peroxide won’t whiten crowns, veneers or fillings, and it won’t fix stains that come from inside the tooth. Talk to your dentist first, especially if you have sensitive teeth, gum disease or a lot of dental work. Dentists can also offer stronger, supervised treatments that work faster.
4. Hair lightening: gradual and drying
A diluted spray can gradually lighten hair over several applications:
- Mix equal parts 3% hydrogen peroxide and water in a spray bottle.
- Spray on clean, damp hair or just a few strands, comb through, and let it dry. Heat or sun speeds the effect.
- Rinse and use a deep conditioner afterward.
Peroxide works by breaking down the pigment in hair, and it also strips moisture, so overuse can leave hair dry, brittle and brassy. Test a small hidden section first, keep it away from your eyes, and stop if your scalp becomes irritated. Avoid it on chemically treated or already damaged hair.
5. Handy uses around the house
Hydrogen peroxide also works as an inexpensive household disinfectant:
- Kitchen and bathroom surfaces: Spray a 50/50 mix of 3% peroxide and water on counters, sinks and toilets. Let it sit for about five minutes, then wipe. Rinse any surface that touches food.
- Grooming tools: Soak nail clippers, tweezers and eyelash curlers to sanitize them.
- Brightening nail soak: Add about 3 tablespoons of 3% peroxide to a small bowl of warm water and soak your nails for about three minutes. Skip it if you have cuts or broken skin around your cuticles, and stop if your skin gets irritated.
- Stains on white fabrics: It can lift some stains, but it can also bleach color, so test a hidden spot first and use it only on white or off-white items.
- Small mold spots: On hard surfaces like tile, grout, tubs and sinks, spray undiluted 3% peroxide on the mold, let it sit about 10 minutes, then scrub and wipe the area completely dry. Even dead mold can trigger allergies, so it needs to be scrubbed away, not just sprayed. Test a hidden spot first, since peroxide can lighten some surfaces.
Mold always comes back unless you fix the moisture behind it, such as a leak, condensation or high humidity. The EPA recommends drying water-damaged areas within 24 to 48 hours. Porous materials like drywall, ceiling tiles and carpet may need to be replaced if they get moldy. If the moldy area is larger than about 10 square feet (roughly 3 feet by 3 feet), or it came from sewage or contaminated water, follow the EPA’s guidance for larger cleanups or call a professional. When cleaning mold, wear long gloves, goggles and an N95 mask. If you have asthma, allergies or other health concerns, check with your doctor before tackling it yourself.
Wear gloves for big cleaning jobs and keep the room ventilated, since peroxide can irritate skin and eyes.
Safety rules for any use
- Stick to 3%. Never use food-grade or industrial-strength peroxide at home.
- Don’t swallow it. If you use a diluted peroxide mouth rinse, spit it out. If a child swallows some, or if anyone swallows a stronger product, call Poison Control at 1-800-222-1222.
- Protect your eyes. If it splashes in your eyes, rinse with running water for 15 to 20 minutes.
- Don’t mix it with vinegar or other cleaners in the same container. Combining them can create a corrosive chemical.
- Store it in its original dark bottle, away from children and pets.
This isn’t a substitute for medical advice. Talk to your doctor or dentist about what’s right for you.
Sources:
- Cleveland Clinic. What to do (and not do) with hydrogen peroxide.
- Mayo Clinic. Cuts and scrapes: First aid.
- Poison Control (National Capital Poison Center). Is hydrogen peroxide safe?
- American Academy of Otolaryngology–Head and Neck Surgery. Updated guideline on earwax (cerumen impaction). 2017.
- U.S. Environmental Protection Agency. A brief guide to mold, moisture and your home.
- U.S. Food and Drug Administration warning on high-strength hydrogen peroxide, via ScienceDaily. 2006.