I have been using Frontline Plus this year - so far, so good.
Sweetie weighs six lbs. - Frontline Plus for 1to 22 lbs.
I usually only use 1/2 of the dose & save the rest for the next time in a
pill bottle, capped. We've seen ticks this year alot on us, but Sweetie hasn't had any, thankfully.
Hope this helps...... When we got Sweetie she only weighed 2.5 lbs. and we used the regular Frontline on her. But I know how it is to worry you are going to hurt your baby with chemicals.
Good Luck.
Cyndi & Sweetie