Tooth whitening is generally well tolerated when carried out or prescribed by a registered dental professional. Some temporary effects are completely normal. Results vary between individuals and depend on the natural shade and structure of your teeth.
Sensitivity: The most common side effect — about 2 in 3 people experience some sensitivity during or after whitening. It is usually mild to moderate and settles within 24–48 hours of completing treatment.
Gum irritation: If whitening gel contacts the gums, they may feel sore or look slightly white immediately after treatment. This settles quickly — usually within a few hours.
Temporary spottiness: You may notice slightly uneven whitening in the first day or two as the colour settles. This usually evens out within 48 hours.
Results: The final shade is best assessed 2 weeks after completing treatment — the colour continues to develop after the last application.
Managing Sensitivity
Sensitivity during or after whitening is temporary. Here are ways to reduce it:
Use a sensitive toothpaste (e.g. containing potassium nitrate) twice daily throughout your course of treatment. Apply a small amount to the trays along with the whitening gel, or use it directly on the teeth after removing the trays.
If sensitivity is significant, take a 1–2 day break from whitening and then resume. You do not need to complete every night without a break.
Avoid very cold or very hot food and drinks during your course of treatment.
Ibuprofen or paracetamol taken before a whitening session can reduce sensitivity during and after the session.
Reduce the amount of gel used or shorten the wearing time if sensitivity is troublesome — contact your dentist for guidance.
The "White Diet" — Foods and Drinks to Avoid
Immediately after whitening, your teeth are temporarily more porous and more likely to pick up staining. For the first 48–72 hours after each whitening session, follow the "white diet":
Avoid:
Tea and coffee
Red wine and dark-coloured soft drinks (cola, fruit juices, energy drinks)
Curry, soy sauce, and other strongly coloured sauces
Berries (blueberries, blackberries, raspberries)
Beetroot and tomato-based sauces
Dark chocolate
Cigarettes and tobacco products
Good choices during this period: water, milk, chicken, fish, white rice, pasta with cream sauces, white bread, banana, apple (peeled), cauliflower, cheese.
Making Your Results Last
Whitening results are not permanent — teeth will gradually return towards their natural shade over time. The following will help maintain your results for longer:
Brush twice daily with a fluoride toothpaste and clean between teeth daily.
Limit staining foods and drinks (tea, coffee, red wine, cola) in your everyday diet, or rinse your mouth with water after consuming them.
Use a straw for cold staining drinks.
Do not smoke — tobacco is the most powerful cause of tooth staining.
If you were given home whitening trays, keep them. Top-up treatments (a few nights of whitening every 6–12 months) are an effective and inexpensive way to maintain your shade. Your dentist can supply additional gel.
Attend regular hygiene appointments to remove surface staining through professional cleaning.
When to Contact Your Dentist
Tooth whitening has an established safety record when carried out as directed. However, contact your dentist if:
Sensitivity is severe or lasts more than 48 hours after finishing treatment
Your gums are significantly sore, swollen, or have not recovered within 48 hours
You notice any unusual changes to the surface of your teeth
You swallowed a significant amount of whitening gel accidentally (in most cases the concentrations used are low and safe, but seek advice if you are concerned)
Important: If you have existing composite bonding, crowns, or veneers, be aware that these materials are not affected by whitening gel and will not change shade. Whitening your natural teeth may result in a colour mismatch with existing restorations — discuss this with your dentist before starting treatment.
Call your dental practice for any concerns. For out-of-hours advice, call NHS 111.
This leaflet is for general information only and does not replace professional dental advice. Your dentist will discuss your individual circumstances and any risks specific to you. Treatment outcomes vary between patients depending on individual circumstances.
When to Seek Urgent Help
Contact your dentist if you experience severe, prolonged tooth pain (lasting more than 24 hours), significant gum irritation that is not settling, or if you accidentally swallow a large amount of whitening gel. Call NHS 111 if you cannot reach your dentist.
References
Aligned with guidance from: FGDP(UK), GDC guidelines on tooth whitening.