Hello bert. The questioner seems to have immediately lost interest in this question, but if by 'active ingredient in some (many) wart removing creams' you mean the ingredient that does most of the removing, I think that is the resorcinol. There is indeed supposed to be some resorcinol in the traditional formula for salycilic acid, though there doesnt have to be much, but without as you say knowing the right strength (as opposed to the Molotov cocktail in wart-removing preparations), I hope I am right in thinking pharmacists in the litigious US are prepared as those in the UK to examine such minor lesions and make recommendations on the strength of their observations. For the US is where I guess the questioner is from.
And that of course goes for all our suggestions. Topical applications are perfectly capable of wreaking havoc, the Chinese 'snake oil' I mentioned being only one of many such.