What do I do?

So both of my cats had fleas and I used Frontline plus on both of them. The older cat doesn’t seem to have fleas but the kitten has fleas more than ever and it’s been 14 days since we used the product on them both and it says to not use it more than once a month. But these fleas are getting worse every day and they’re biting his face. I want to use the frontline again but he’s only 5-6 months old and I don’t know if that’s even safe to do.

UPDATE: The lady had told us all we have to do is get luke warm bowl of water w blue dawn soap let a rag soak in it put the rag on his face then wash his body and that should kill them all.