Like what? You mean you making it yourself or buying it? They can probably be a lot more dangerous than those manufactured, because they don't come with instructions, but that is if you use dangerous chemicals which you really have no clue of in which ratio to use. Then you can also get other things that you use (my boyfriend mentioned chillis) and I think that is ok and can be very effective.
Yes, there are many herbal remedies for keepings pests away that work fantastic. Rosemary keeps fleas away, Tea tree oil keeps lice away, etc. IMO, there is no reason to use toxic poisons when the Earth has given us so many natural remedies.
I am referring to my own preparation of pesticides