Interesting question ,you could try asking the technical helpline at Novartis , I tried asking why when you pour it in a line down the spine it spreads all over the body via the lanolin and yet when you spray it for blowfly it only protects where it touches , 3 different people couldn't give me an answer ?? clik and clikzin with fleecebind is easy to get information . I use spot-on for ticks and I'm told many use crovect ,then apply clik on top for blowflys , seems to work ok