We just switched from Trifexsis (pill) to Advantage Multi after hearing that the pill may be causing issues in small breeds. The front desk people at the vet said to only bathe P-Nut 2x a month or we'd be washing the topical off. Let me just say that will not work for us.
So I went to the manufacturer and they said the dog can bathe/swim 90 minutes after application; the product will still be effective. We did our first application today - we'll see how it goes!