Peroxide explained: safe or not?

Professional whitening uses hydrogen peroxide (H2O2) or carbamide peroxide. Carbamide peroxide is a slower-releasing variant that breaks down in your mouth into roughly one third hydrogen peroxide. Both are colourless and act as mild oxidising agents.

In the European Union only a dentist may apply products with up to 6% hydrogen peroxide (or equivalent). Anything above that is banned for consumer use. Products from webshops or outside the EU regularly sit well above that limit, without any appropriate guidance.

Peroxide passes through the enamel into the dentine layer, where most of the colour actually sits. There it splits the large coloured pigment molecules into smaller, colourless particles. The tooth structure itself stays intact: only the colour components change.

This process is chemical, not mechanical. No enamel is scrubbed away, unlike what some aggressive whitening pastes do. Scientific reviews from bodies such as the FDI and Cochrane consistently show that teeth do not lose strength when whitening is done under professional supervision.

The most common side effect is temporary sensitivity to cold. During the treatment peroxide makes the enamel slightly more permeable, so cold reaches the nerve faster. Gums may also briefly turn a pale white where gel touches them.

Both effects are reversible. Within a few days after the last treatment the enamel fully closes again and the sensitivity fades on its own. Extra fluoride, a toothpaste for sensitive teeth and slightly shorter daily wear times help dampen sensitivity along the way.

At Zonnelach we deliberately choose gel with added fluoride and potassium nitrate. This reinforces your enamel during the treatment and actively limits sensitivity. For people with sensitive tooth necks we tailor the schedule and concentration individually.