Are there any side-effects from using Wartner Wart & Verruca Remover?

There are a number of possible side-effects:

As with all freezing methods, the skin may turn white temporarily.
A blister develops under the wart, but this is part of the treatment and is harmless.
Using Wartner Wart & Verruca Remover may cause some discomfort.
Applying the foam applicator to the wart or verruca for too long may lead to local tissue death. You should therefore follow the instructions carefully and apply the treatment for the time specified based on the size of the wart or verruca.
Always use Wartner Wart & Verruca Remover very carefully and accurately. If you’re not careful, scars and nerve damage may occur.