Hydrogen peroxide is the antiseptic that fizzes on contact with a cut. It is used for cleaning wounds, as a mouthwash, and for softening earwax. Modern wound care advice has moved away from putting it on healing wounds — the same reaction that kills bacteria also damages the cells doing the repairing.
What is Hydrogen Peroxide?
Hydrogen peroxide is a general-sale antiseptic, sold in pharmacies as a solution — usually 3%, sometimes expressed as 10 volume. Stronger concentrations exist for industrial, cosmetic and hair-bleaching use and are not for wound or mouth care.
Because it is a general-sale product rather than a scheduled medicine, plain hydrogen peroxide is not listed in its own right in the South African Medicine Price Registry.
(A search of that register for “peroxide” returns benzoyl peroxide products — acne creams and gels such as Acneclear, Clindoxyl and Epiduo. Benzoyl peroxide is a completely different substance used for acne, and none of those results is hydrogen peroxide. Disregard them if you search the register yourself.)
The chemistry is simple and explains everything about it. Hydrogen peroxide is water with an extra oxygen atom, and it is unstable. On contact with blood or tissue, an enzyme called catalase breaks it apart into water and oxygen — that is the fizzing. The released oxygen damages bacterial cell walls and proteins.
The problem is that this is not selective. The same oxidising action that damages bacteria damages fibroblasts and the new cells building granulation tissue. It also does not distinguish between a dirty wound and a clean one that is healing well.
That is why the advice has changed. Hydrogen peroxide remains a useful antiseptic for specific purposes, and repeatedly pouring it into a healing wound slows healing down.
What is Hydrogen Peroxide commonly used for?
Where it is still reasonable:
- Initial cleaning of a dirty wound — a grazed knee with grit in it, a wound with visible debris. A single cleaning is a different matter from repeated application.
- Loosening dried blood, crusts and stuck dressings, where the fizzing helps lift material away.
- Mouthwash, diluted, for mouth ulcers, gum inflammation and after some dental procedures — on a dentist’s advice.
- Softening earwax, in preparations formulated for that purpose.
- Disinfecting surfaces and non-porous equipment.
- Removing blood stains from fabric.
Where it is best avoided:
- Routine cleaning of clean cuts and grazes. Running water is better, and gentler.
- Repeated application to a healing wound, which delays healing.
- Deep or puncture wounds, and any closed cavity. Oxygen released inside a closed space cannot escape freely, and gas can be forced into tissue.
- Surgical wounds, unless a clinician has specifically said to.
- Large burns.
For an ordinary cut or graze, the current advice is unglamorous and well supported: rinse it under clean running water, remove any visible dirt, pat it dry, and cover it. A wound kept clean and covered heals faster than one that is repeatedly disinfected. If an antiseptic is wanted, a modern one such as povidone-iodine or chlorhexidine is gentler on healing tissue.
How Hydrogen Peroxide fits into this medicine category
| Group | Examples | Notes |
|---|---|---|
| Oxidising antiseptics | Hydrogen peroxide | Fast-acting; also damages healing tissue |
| Modern antiseptics | Povidone-iodine, chlorhexidine | Effective and gentler on wounds |
| Saline and clean water | Sterile saline, tap water | First choice for cleaning most wounds |
| Topical antibiotics | Fusidic acid, mupirocin | For established bacterial infection |
| Antifungals | Clotrimazole (Canex V) | Fungal infection |
| Topical steroids | Betamethasone (Clomaderm) | Inflammation — never for infection alone |
Hydrogen peroxide’s place has narrowed rather than disappeared: it is a cleaning agent for dirty or crusted wounds and a diluted mouth rinse, not a routine wound treatment. See the skin and wound care hub.
What to check before using Hydrogen Peroxide
- Check the concentration. Use 3% (10 volume) for wound cleaning and mouth care. Anything stronger — the concentrations sold for hair, cosmetic or industrial use — can cause serious chemical burns and must never be used on skin, in the mouth or in the ear.
- Dilute it for mouth use, typically half and half with water, and do not swallow it.
- Do not use it in the ear if you have or might have a perforated eardrum, grommets, ear surgery, or discharge from the ear. Use only a product intended for ears.
- Keep it out of the eyes. If it splashes in, rinse with plenty of water for at least fifteen minutes and seek medical attention.
- Do not use it repeatedly on a healing wound, and do not use it on deep or puncture wounds, or in a closed cavity.
- Do not use it on animal or human bites — those need medical assessment, not home antiseptics.
- Store it in its original dark bottle, away from light and heat. It decomposes, so old solution may do little.
- Do not mix it with other cleaning products, particularly anything containing chlorine or ammonia.
- Keep it away from children. Swallowing concentrated hydrogen peroxide is dangerous.
Possible cautions and when to ask a pharmacist or doctor
Ordinary 3% solution on intact or lightly broken skin usually causes stinging, temporary whitening of the skin, and irritation. The whitening is a normal effect of the oxygen release, not a burn.
Used in the mouth, it can cause irritation, a furry-tongue appearance and mouth soreness with repeated use. Do not use it as a long-term daily mouthwash without dental advice.
Get emergency help for:
- Swallowing hydrogen peroxide, particularly a concentrated solution. Take the bottle with you.
- Splashes in the eye — rinse thoroughly with water first, then seek care.
- Chemical burns — blistering, white or grey discolouration, or severe pain after contact with a strong solution.
- Swelling of the face, lips or tongue, or difficulty breathing.
See a doctor for a wound that:
- Is deep, gaping, or will not stop bleeding, or may need stitches.
- Is a puncture wound, or from an animal or human bite.
- Contains debris you cannot remove.
- Becomes red, hot, swollen, increasingly painful, or oozes pus, or develops red streaks spreading from it.
- Comes with fever or feeling generally unwell.
- Is not healing after a couple of weeks.
- Occurs in someone with diabetes, poor circulation or reduced immunity, where wounds need earlier and closer attention.
Also ask about tetanus — any dirty wound, puncture wound or bite is a reason to check whether your vaccination is up to date.
Related medicine guides
Frequently asked questions
What is hydrogen peroxide used for? Cleaning dirty wounds, loosening crusts and dried blood, as a diluted mouthwash for ulcers and gum inflammation, and for softening earwax in products made for that purpose.
Should I put it on a cut? For a clean cut or graze, rinsing under running water is better. Hydrogen peroxide is reasonable for an initial clean of a dirty wound, but repeated use slows healing.
Why does it fizz? An enzyme in blood and tissue breaks it into water and oxygen. The bubbles are the released oxygen.
Which strength should I buy? 3%, also labelled 10 volume, for wound and mouth use. Stronger cosmetic or industrial solutions can cause chemical burns.
Can I use it as a mouthwash? Diluted, and short-term, for ulcers or gum inflammation — ideally on a dentist’s advice. Do not swallow it or use it daily long-term.
Can I put it in my ear? Only a product formulated for ears, and never with a perforated eardrum, grommets or a discharging ear. Ask a pharmacist.
Is it the same as benzoyl peroxide? No. Benzoyl peroxide is an acne treatment found in creams and gels. They are different substances with different uses.
Does it whiten teeth? Peroxides are used in dental whitening, but at controlled concentrations by dental professionals. Home use of the antiseptic solution for whitening risks gum and enamel damage.