I used the Pro Effects Crest White Strips - they work but boy do they hurt!

I used the first lot one afternoon and they felt fine, no pain to my teeth or gums and my teeth were definitely brighter.

I then didn't get around to using them for a couple of days so when l did l did as the packet suggested and used them twice in one day. BIG MISTAKE. The first lot [done in the morning] were fine but the second lot - right before bed - my god l woke up in agony. My teeth hurt so much l could not sleep! l took painkillers but still woke up every hour or two in huge pain. The next day l couldn't eat anything hot or cold and brushed my teeth [electric toothbrush] very gingerly with Pronamel paste [gentle]. The pain eventually went away by the evening - 24 hours after l used them.

A few days later l tried again [midday] and they seemed to be fine, no pain and teeth definitely getting whiter. A few days after that l used them again, this time about an hour before l brushed my teeth and went to bed. Woke up in agony again. Horrid! It wasn't my gums that were sore though, my actual teeth ached and were super sensitive.

I think l am going to stop using them for a few weeks or even months now - my teeth are definitely whiter so l am in no hurry. l think the problem may be using them at night and brushing so soon after, your teeth are obviously very weak/vulnerable as a result.

Next time, if there is one, l will do them mid morning and see if that is any better.