Rash in Skin

Question
HI MARJORIE,
I noticed my bulldog scratching and found a tick on her as well. So, I purchased Frontline Plus for dogs weighing 44-60 lbs. As soon as I put it on her shoulders she started scratching more aggresively but this time she would literally thrust herself on furniture, anything, that would give her relief. Then, she started caughing and vomited a white mucousy substance. I figured immediately that frontline was the cause of this. So, I called them and they told me this was vey weird behavior and that the product had been tested in many other dogs with not signs like that of my bulldog.  She told me that maybe the fleas and ticks were dying or just being more aggresive on her skin. That sounded right to me so I just kept helping her by scratching her in areas she couldn't reach. Two days later, I noticed a thick crust forming and looking closer it was apparent some pus forming inside. I'm so upset at this I don't even know where to start. It's my fault for giving her this product. I don't know what to do. I only wanted to help her get rid of the fleas and ticks but ended making her problem worse. Sadly, her flea problem is still there.  I noticed her scratching a while ago...
My fear is that we suspect that she might be pregnant. Frontline assured me that her pregnancy would not be affected. Would you know about this?

Answer
First of all, not all dogs are the same. Some react differently to medications as you have just experienced. This could be due to the fact that she is pregnant. My vet will not use any product on a pregnant female, period, no matter what they say. Of course Frontline is going to say the product is safe. You've already used it.

There is a product called CapStar which is safe for pregnant females and will kill any live fleas, not eggs, on a dog in 30 minutes. If she has a huge infestation, this would work well initially to kill the adult fleas. It's so safe, you could use it once a week if you wanted to.

None of this is your fault. You're not the vet. I would just try to make her as comfortable and flea free until she has her puppies, or not.