Do whitening strips damage your enamel?

Used as directed, whitening strips have not been shown to do lasting harm to enamel in the research we could find, but that research is thinner than it sounds. The trials in people mostly measured colour and side effects over weeks, and the Cochrane review of home whitening found the common side effects were tooth sensitivity and oral irritation, which it describes as “mild and transient”. What happens to the enamel itself has mostly been measured on extracted teeth in a laboratory, where a 2026 meta-analysis found a small loss of surface hardness. And the strength of the product depends on where you live: in the EU and UK, anything sold in a shop is capped at 0.1% hydrogen peroxide.

What the trials in people found

The best summary is the Cochrane review, updated in 2018. It pooled 71 randomised trials of home whitening, including hydrogen peroxide strips, trays of gel and paint-on gels. Against a placebo, the products did whiten teeth “over a short time period (from 2 weeks to 6 months)”, but the certainty of that evidence was rated low to very low, and only two of the 71 trials were at low overall risk of bias. On harm, the review is specific: “Tooth sensitivity and oral irritation were the most common side effects which were more prevalent with higher concentrations of active agents though the effects were mild and transient.”

The strip trials give a sense of scale. A US safety assessment of hydrogen peroxide as a cosmetic ingredient, by the Cosmetic Ingredient Review panel, summarises a pooled database of trials of 6% hydrogen peroxide strips used twice a day for two weeks: oral irritation in 22% of people on average, tooth sensitivity in 20%, and “In virtually all circumstances, adverse events were transient in duration.” A 2024 review of 88 studies of over-the-counter whitening reached the same place, listing “tooth sensitivity, gingival irritation, and enamel surface changes” as the adverse effects, and noting that strips were the over-the-counter product with the most support from clinical trials.

None of those trials was designed to find slow damage to enamel over years. That is a gap in the evidence, not evidence of harm, and it is the honest reason the answer to the headline question starts with “not shown” rather than “no”.

What about the enamel itself?

Most of what is known here comes from laboratory tests on extracted teeth, where hardness is measured before and after bleaching. The 2026 meta-analysis found 81 such studies that met its criteria and could pool nine. Pooled, bleaching left enamel slightly softer at the surface, about 11% on average, and the authors describe the change as “statistically detectable but small, outlier-sensitive”, without clear evidence of a clinically meaningful effect. They add their own limit in the same breath: “Within the limitations of in vitro evidence”. A tooth in a lab has no saliva, no pellicle and no remineralisation going on around it, so these numbers can overstate or understate what happens in a mouth; nobody yet knows which.

England’s prevention toolkit takes a cautious line for one group. In its tooth wear chapter, Delivering better oral health lists “tooth whitening materials” among the chemical factors to consider in someone whose teeth are already wearing, and suggests “Consider alternatives for whitening in dental practice”. If your enamel is already thin, that is a conversation for a dentist before a box of strips.

Why peroxide and acid are different problems

Peroxide does not scrape the tooth. The American Dental Association describes carbamide and hydrogen peroxide as agents that “can readily permeate dental hard tissues”: they pass through the enamel and break down the coloured molecules inside, which is why bleaching changes the shade of the tooth itself rather than polishing its surface, as natural teeth whitening explains. Acid is another matter. Lemon juice, vinegar and the acidic home recipes that circulate online dissolve the mineral at the surface, and enamel lost that way does not come back — see what causes enamel erosion. Of the two, the one with a clear mechanism for permanent loss is the acid.

The strength depends on where you live

In the EU, hydrogen peroxide in oral products is set by Council Directive 2011/84/EU, and the UK kept the same entry in its retained cosmetics regulation. The rules have three tiers:

• Up to 0.1% hydrogen peroxide, present or released, in any oral product, including toothpaste and whitening kits sold to the public.
• Above 0.1% and up to 6% only for tooth whitening products that are “only sold to dental practitioners”, with the first use of each cycle by a dental practitioner or under their direct supervision, and “Not to be used on a person under 18 years of age.”
• Above 6%: not permitted in these products at all.

Carbamide peroxide counts too, because the limits apply to hydrogen peroxide “present or released”. In the United States the picture we could document is different. The ADA says over-the-counter whitening products contain peroxide “at lower concentrations than in-office or dentist-prescribed, at-home bleaching techniques”, and whitening strips are among the products that can carry its Seal of Acceptance. The strips in the published safety trials summarised above carried 6% hydrogen peroxide. We did not find a single federal percentage limit for US strips equivalent to the EU’s, and this page does not claim one exists.

Peroxide-free kits

With a 0.1% ceiling on anything sold in a shop, some kits sold in Europe whiten without peroxide at all, using colour-correcting pigments or other actives. The evidence behind them is thin. A 2025 systematic review of peroxide-free colour correctors found six studies: one clinical trial and five laboratory studies. Those reported little change to enamel and sensitivity in under 3% of people, but also a smaller colour change than carbamide peroxide. In a 2023 laboratory comparison of five peroxide-free over-the-counter kits on stained cattle teeth, the performance “differed vastly from one brand to the other”, and overall they were less effective than a 16% carbamide peroxide gel. Gentler, probably; proven, not yet.

Who paid for the trials

The Cochrane review records a funding source for each of its 71 trials. We counted them from its tables. 50 name a company as funder, or say the authors work for one; one names a government research grant; the other 20 say funding was not reported, or name none. Of the 22 trials whose interventions included whitening strips, 18 name a company: 17 Procter & Gamble, fully or in part, and one Colgate-Palmolive. The review itself was funded by the UK’s National Institute for Health Research through Cochrane, and each of its authors declares “none known”.

A manufacturer paying for a trial does not make the trial wrong; it is context the reader is entitled to see next to the finding. Every paper cited here has a row in the trial funding ledger, with its funding statement quoted rather than summarised. Three of those statements sit behind a paywall or a bot check we do not get around, and the ledger says so.

If you use them

• Follow the timing on the box. The side effects in the trials rose with concentration, and the results people got came from the schedules the trials used.
• Crowns, veneers and fillings will not change colour. The ADA is plain that “only natural teeth will be affected by the bleaching agent”, so a whitened tooth can end up lighter than the crown next to it.
• If your teeth are sensitive already, a 2015 meta-analysis found that potassium nitrate and sodium fluoride reduced sensitivity during bleaching. How those actives work is set out in toothpaste for sensitive teeth.
• Pain that lingers, or a single tooth that hurts, is not a whitening side effect to wait out; what causes sensitive teeth covers the patterns that need a dentist.

How we made this page

We read the Cochrane review in full, including its tables of included trials, the abstracts of the other reviews, the text of the EU directive and the UK regulation, and the ADA’s own summary. We did not test any product, and nothing here is personal advice: a dentist who has looked at your teeth can tell you whether whitening suits them. We don’t link to shops from this page and earn nothing from it.

Fig. 1 is free to reuse under CC BY 4.0 — see the diagrams page.

References

1. Eachempati P, Kumbargere Nagraj S, Kiran Kumar Krishanappa S, et al. Home-based chemically-induced whitening (bleaching) of teeth in adults. Cochrane Database Syst Rev 2018;12(12):CD006202. DOI · PubMed · Funding: see ledger
2. Márton P, Antal M, Kiss-Dala S, et al. Enamel damage from tooth-whitening — a systematic review and meta-analysis. J Dent 2026;172:106786. DOI · PubMed · Funding: see ledger
3. Cosmetic Ingredient Review. Safety assessment of hydrogen peroxide as used in cosmetics (draft report for panel review, 2018). Official page, accessed 23 Sep 2026.
4. Barbosa LMM, Amâncio Filha MBG, Leite JVC, et al. Over-the-counter products in tooth bleaching: a scoping review. J Dent 2024;145:104989. DOI · PubMed · Funding: see ledger
5. Office for Health Improvement and Disparities. Delivering better oral health: an evidence-based toolkit for prevention (chapter 7, tooth wear). Official page, accessed 23 Sep 2026. · Funding: see ledger
6. American Dental Association. Oral Health Topics: Whitening. Official page, accessed 23 Sep 2026.
7. Council Directive 2011/84/EU of 20 September 2011 amending Directive 76/768/EEC, concerning cosmetic products, for the purpose of adapting Annex III thereto to technical progress. Official Journal of the European Union L 283, 29.10.2011, p. 36–38. Official page, accessed 23 Sep 2026.
8. Regulation (EC) No 1223/2009 on cosmetic products, Annex III, entry 12 (hydrogen peroxide), as retained in UK law. Official page, accessed 23 Sep 2026.
9. Boruga M, Tapalaga G, Luca MM, et al. Hydrogen peroxide-free color correctors for tooth whitening in adolescents and young adults: a systematic review of in vitro and clinical evidence. Dent J (Basel) 2025;13(8):346. DOI · PubMed · Funding: see ledger
10. Grillon M, Di Bella E, Krejci I, et al. In vitro evaluation of tooth-whitening potential of peroxide-free OTC dental bleaching agents. Dent J (Basel) 2023;11(4):89. DOI · PubMed · Funding: see ledger
11. Wang Y, Gao J, Jiang T, et al. Evaluation of the efficacy of potassium nitrate and sodium fluoride as desensitizing agents during tooth bleaching treatment — a systematic review and meta-analysis. J Dent 2015;43(8):913–923. DOI · PubMed · Funding: see ledger