The two active ingredients in Frontline ARE approved for use in food animals. The active ingredients are fipronil and (s)methroprene.
Fipronil is approved for use in cattle, sheep, and chickens: http://parasitipedia.net/index.php?option=com_content&view=article&id=2465&Itemid=2733
And (s)methroprene is approved as a feed additive for beef cattle and is also in poultry houses: http://smartlic.com/products/ne-30-igr-fly-control/
In addition permethrins are a toxin and can cause a severe reaction in some small animals, it is also one of the leading causes of fatal poisoning in cats.
I find preventing an infestation to be a heck of a lot easier than trying to eradicate one with DE or permethrins or even gasoline in the case of leg mites. I also believe this method is much less stressful for the birds, my chickens are pets first and egg producers second. In addition my area has a lot of ticks that carry a variety of really serious diseases, neophyte ticks often feed on birds.
Parasitepedia is a good link , I have shared it many times myself. The link clearly states that fipronil is used on cattle in Latin America , yet not Australia or the U.S. .
Fipronil is effective against horn fly and ticks, neither of which afflict chickens.
When using products approved for herbivores and ruminants it's difficult to translate the dosage to chickens as they don't have multiple stomachs, nor to they share similar anatomy. As the seed for each and every egg that a pullet will hatch in her life time is present in her system from day of hatch, I would say that it is fair to say that there is a likelihood that traces of any chemical you use might find its way into the egg.
My point is , there are poultry products on the market that have been tested , so why take the risk ?
The most recent class of pesticides are spinosad based and are available in the U.S and UK and used within the poultry industry.