I've always been a bit leery of pre-treaters since -- for whatever reason -- they're obscenely expensive and hardly ever work.  This one is the exception to the rule.  Our dog ripped her nail off (OUCH!) and left bloody little footprints all over the house.  We used this, hit it with the carpet shampooer, and there's absolutely no trace.  I've tried a bunch of these, and this is by far the best one I've used.  No more searching!