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Personal care · product guide

Teeth whitening: does it work?

Peroxide strips and gels do lighten teeth, at the cost of temporary sensitivity. A cosmetic choice with no health benefit.

Moderate evidenceReviewed September 2026

What it is

Teeth darken from surface stains (coffee, tea, wine, tobacco) and from changes inside the tooth with age. Bleaching products use hydrogen peroxide or carbamide peroxide (which breaks down into hydrogen peroxide) to lighten the tooth's own color: whitening strips, paint-on gels, tray gels from a dentist, and in-office treatments. Stain-removal products such as whitening toothpastes and 'accelerators' polish off surface stain without changing inner color.

Bleaching doesn't lighten crowns, veneers or fillings, so results can look uneven if you have visible dental work. The hydrogen peroxide active page covers strengths and safety.

How strong is the evidence?

Moderate evidence

A 2018 Cochrane review of 71 trials found home peroxide products whitened teeth versus placebo over 2 weeks to 6 months, but the certainty was low to very low and it could not say which product, strength or schedule is best. Tooth sensitivity and gum irritation were the common side effects, more frequent at higher strengths, and mostly mild and temporary. Most trials were short and many were manufacturer-sponsored.

The claims you'll see, checked

Peroxide strips and gels whiten teeth

Holds up

Consistent whitening versus placebo in short trials, though evidence certainty is low.

Whitening damages enamel

Mixed

At home-use strengths used as directed, serious enamel damage isn't shown in trials; long-term data are limited and overuse raises risk.

Charcoal and baking soda whiten safely

Unproven

They only scrub surface stain, and charcoal products lack evidence for safety or efficacy.

LED lights speed up home whitening

Unproven

Evidence for added benefit from consumer lights is weak.

Results are permanent

False

Color gradually relapses over months, faster with coffee, tea, wine and smoking.

What to look for

  • Hydrogen peroxide or carbamide peroxide as the listed active if you want an actual shade change.
  • Lower-strength products used longer if you have sensitive teeth.
  • A dental check first if you have decay, gum disease, exposed roots, or front crowns and fillings that won't change color.
  • A potassium-nitrate or stannous-fluoride toothpaste during whitening to limit sensitivity.

What to skip

  • Charcoal powders and DIY abrasives.
  • LED gadgets sold as the key ingredient.
  • Unbranded high-strength gels bought online, which may exceed legal peroxide limits.
  • Whitening more often than the label says to chase a brighter shade.

How to use it

  • Follow the label's wear time and course length exactly.
  • Brush and floss before applying strips so the gel contacts clean enamel.
  • Avoid staining foods and drinks for a few hours after each session.

Who should be careful

  • Expect temporary tooth sensitivity and gum irritation; pause or use a lower strength if it's bothersome.
  • Not advised during pregnancy or breastfeeding, or for children and teenagers, without dental advice; the EU limits over-the-counter products to 0.1% hydrogen peroxide and restricts stronger ones to dental supervision for adults.
  • Keep gel off the gums and don't use on broken or inflamed gums.
  • Sudden darkening of a single tooth needs a dentist, not bleach; it can signal a dying nerve.

The studies

Every citation is checked against its PubMed record.

  1. Home-based chemically-induced whitening (bleaching) of teeth in adults
    Eachempati P, Kumbargere Nagraj S, Kiran Kumar Krishanappa S, Gupta P, Yaylali IE · Cochrane Database of Systematic Reviews · 2018 · Systematic review

    71 trials: home peroxide gels, strips and other bleaching products whitened teeth versus placebo over 2 weeks to 6 months, with low- to very low-certainty evidence and no reliable way to rank products. Sensitivity and oral irritation were the most common side effects, more common at higher concentrations, and mild and transient.

  2. Charcoal and charcoal-based dentifrices: A literature review
    Brooks JK, Bashirelahi N, Reynolds MA · Journal of the American Dental Association · 2017 · Literature review

    118 articles screened; no clinical trial met inclusion criteria, and some reports described harms such as enamel abrasion. The authors found insufficient evidence for the safety and efficacy claims of charcoal toothpastes and powders.