Couple of questions... Can you see them? How often can you use the spot-on? Lincoln was scratching quite a bit and me and my partner were getting bitten. We thought our bites were from being out in the garden as our back garden is a state at the moment as there was a huge stagnent smelly concrete pond which we have now got rid of but there were lots of flies and bugs around it so we thought our bites were from that. Because of Lincolns itchy-ness we got some spot-on and he stopped scratching and our bites went away. This was only two weeks ago, and the stuff says for coverage of 4 weeks. He has already started scratching again and Simon has started to be bitten again. Can I use more spot-on now, or is it too soon?