black lab biting her nipples

Question
I have a 1 year old black lab female that is developing nipples and sacks under the back 4 nipples but she keeps biting them she just got frontline applied about 2 weeks ago and hasn't ever been around a male for possible breeding. Please help!

Answer
Was the dog recently in heat?  Nipples will develop during the heat cycle and be more apparent afterwards.  Some dogs are just naturally "baggy" in their mammary area.

Why she is biting them, I don't know.  We don't use Frontline as we are not in a Flea area, but typically that's applied to the back and should not affect the belly area.  

I would take the time to fully wash her belly to make sure that it's clean.  If you live in a wintery area of the country, she could have de-icing salt on her belly and it's irritating.  

If you notice any sores or scabs though, I would take her to the vet. You may also want to call the vet to find out if where you live is a bad area for fleas this time of year and if you need to use Frontline year round.  I personally only like to use those poisons when absolutely necessary.  Like mine ONLY get Heartworm preventative during the summer months.