Allergic reaction to Advantagell

One of my cats had a severe reaction to Advantagell . He lost a lot of fur and I'm wondering how long will it take to grow back? Does anyone have experience with this problem?

 I had been using Frontline  on my 4 cats whenever a flea problem occurred . The last time I used it which was last June one of my cats still continue to scratch. Also he was licking his fur off his stomach and the back side of his body. So I thought maybe he still had fleas. The other three weren't scratching though, now upon retrospect I think he was having an allergic reaction to  the flea treatment , but at the time I didn't realize this so in August I put Advantage ll on him and within a week I could see  he was having  a very bad reaction. All the hair fell out on the spot where I put the treatment, also with each day more hair fell out in clumps and sections  his skin was a deep maroon . His skin didn't become raw but was a deep red. By the end of the month he had lost all the hair from his shoulder to his backside ,including his tail. He is a Maine Coon cat and has long hair so he ended up looking like a lion with a mane because it didn't affect the hair above the shoulders or his face and front paws. As soon as the  reaction became evident I researched online and found that many cats and dogs had bad reactions to Advantage ll  . I also learned that coconut oil can help heal their skin. So I began applying coconut oil to his whole body every day and saw improvement right away. His skin returned to a normal color within a week , but it's taken a long time for the hair to grow back. His tail used to be very bushy , but it only has fuzz now. I will never use any spot on treatment again. It's not worth the risk. I have nursed him through this,and  even though he is recovering , I know it made him sick. I could see it in his eyes. He slept a lot and also ran a temperature. He did keep eating though so no problems there.  It's been nearly 2 months and the worst is behind him but I'm just wondering how long it will take for the hair to grow back ? I will only use natural treatments from now on. The first picture shows before and the 2nd one is the way he looks now. Is there any nutrient I can give him that would help restore his fur ?

I have never heard of any reactions to plain Advantage, and only a few to Advantage II, though none so severe as yours.  I have heard of LOTS of reactions to Advantage Multi, both skin problems and neurological ones so I will not use it myself, but a friend uses it on her two Maine Coons and has no problems.  The licking of fur off the tummy and backside is definitely an allergic reaction, although that can be to many things.  I have one that does that every fall and has to get a steroid injection (depo-medrol) which lasts one month and yet he doesn't need it again for another year.  Hopefully his tail will grow fuzzy again during the winter months, because that's when they naturally grow a heavy coat. 

It's fine not to use another spot-on but be very careful with any flea control medicines that are injected or taken internally, and I would advise against trying any brand new product that has not had enough time to show its true colors long term.  Frontline has been safe for years, but fleas have developed some resistance to it, so possibly your cat has developed a sensitivity to it.  I would be very careful using ANY flea products on him as it seems he may have a very sensitive system.  You may have to resort to what we did in the old days, flea combing and bathing on a regular basis.

I had teh same thing happen to my long haired boy when I used Advantage Multi. I used it on 6 other cats with no problems, but most of his hair fell out, and he itched for a long time.  It does take a couple of months for the hair to grow back, just like when they are shaved for surgery. He is fine now, but loved coming into the house because winter was coming and he had no hair! I can't get him back outside now!