The classic spot on that we use monthly to protect our dog and cat from ectoparasites are absorbed and conveyed by the lipid film that covers the skin of our four-legged friends: for this reason the habit of applying the spot on immediately after bathing is wrong!
Better to wait a few days when the lipid film has reformed and the medicine can be completely absorbed and therefore the treatment will be effective in protecting against ticks, fleas and phlebotomy.