Big lump bump with scabs under chin?

I have a short hair domestic male named Mario who is about 10 yrs old. We live in an Apartment. He's completely indoor. He's on a dry food diet of Blue. The first thing I noticed was he was scratching all night long. There were nights where I would wake up at 2am and brush him for a long time because I could tell how uncomfortable he was. I changed the bedding and it still happened. I thought it has to be fleas. Even though I could not find a single one. When I would brush him so much hair would come out along with a ton of white flakes. First I tried vitamins for dry skin. He couldn't keep them down. So I put him on frontline about 6 weeks ago. ( I also switched his food from the high protein to the weight loss. I didn't notice much of a difference other than more fiber, fat, protein and omegas. Both are grain free. But maybe this is an allergy. )
Then 2 weeks after that I gave him a bath with flea medicated shampoo. I noticed a big difference with the shedding and white flakes. I gave him his second dose of frontline a week ago. It was a week late from when I was supposed to. I was debating whether or not to give it to him but he was still scratching. My main concern is that I noticed a huge bump on his chin. At first I thought it was under his skin. It felt more like a lump. But there is a scab on it. This showed up after the first frontline and shampoo. Then after the second dose of frontline another big lump/bump with a scab showed up on his neck. I'm wondering if he is actually having a reaction to the frontline and if I should get a normal cat shampoo and give him a bath. After I put the frontline on the second time he was really trying to get to it. Trying to lick it off. I had to stop him a few times. I put in between his shoulders in a couple areas but what if he got to it? This may sound so petty.
But stuff like this has never happened before. He has the silkiest coat of fur. I always assumed that it meant he was healthy. He has pink ears, gums, etc. I thought I would try online before going to the vet. I called them and they were not helpful.

Since it's under his chin, I'm wondering if it's chin acne.  If you are using plastic dishes, change them to ceramic or stainless steel and wash them daily.  You can clean his chin with Hibiclens daily (ask for the pharmacist to show you where it is) or consider using Stridex pads.   Also, you need to get him to the vet to make sure that nothing is infected and that he doesn't have something else going on. 

I use ceramic. He uses the same dishes I do and they are raised off the floor. He drinks brita water. I rinse his bowls daily. I got a picture of it. I also got video. Just trying to figure out how to post it. I did make an appointment with the vet. I could see how the one on his chin might be acne but the one on his neck is scary looking. I hope I'm able to post this pic. Thank you for responding.

He acts completely normal. Eats and drinks as usual. Playful as ever. He doesn't even seem to know it's there. I think I'm just as scared of going to the vet as my cat is lol.

Hi Tif Joyce.Cats can have allergic reactions to almost anything.My one kitty Milo when using advantage would lose all his hair in the areas where I administered the advantage.My other 7  not a problem.So yes, but even one flea for some cats which would be extremely hard for you to find can cause havoc with a cat with itching even though the flea is now in the carpet or whatever.People assume when using say a flea comb a  cat has to be loaded with fleas.Not.With some they have an allergic reaction to just one bite.I would see a vet to try to determine the cause myself.Do you use a flea comb? If so do you see any flea dirt? These bumps when you feel them do they feel like they are attached in a way that you can't move them from side to side or do they move as you move the skin with them? C.

I would really get him to the vet.  It might have been an abscess that's burst or any other number of things. 

I have an appointment for tomorrow morning. Fingers crossed. Thank you for taking the time to respond. I'm so nervous. He's been the only constant in my life in the last decade. Here's a picture of my baby. Not sure where we post them on here.

He's a cutie!!  Hope all goes well at the vet's tomorrow!  Keep us posted.

This turned out to be a scratch! Since he has been overly itchy he must have really punctured himself. The vet gave me steroids. 5mg of prednisone to give him 2x daily for 4 days and 1x daily for 4 days. And I the meantime I'm supposed to get him off the weight loss formula food and back to the normal food. I found that interesting but she said that the weight loss stuff is high in fiber, which I noticed and I thought would make him poop more, therefore lose more weight. But she said cats aren't supposed to have that much fiber. It's better to feed them high protein, like 40-44%, and a strict diet 3/4 cup per day diet. Mario is 19.4 pounds (eek! I know) I have been giving him about 1 1/3 per day. I'm also supposed to continue the flea treatment and basically find out what is making him itchy. The vet also gave me antibiotics but I chose not to get them because one pill right now is enough. If anyone thinks I should go back and get it please say something. Mario has started sleeping through the night again, which means I sleep through the night! It has been so lovely Thank you again for your help. I really appreciate it.

MomofMaxwell, could you use another flea medication on Milo other than Advantage? Or did he react the same to all flea medication?

I was wondering if I could get your opinion on one more thing. Whether I'm grasping at straws or this may be a logical explanation as to what is making my cat sick...
Two months ago my upstairs neighbors were evicted. They had two cats and their apartment was the most vile thing I have ever seen. Food stained the walls, carpet worn down to pad, cat poop embedded in what little carpet was left, holes punched through walls and doors. I can only imagine what kind of diseases those poor cats carried. Maintenance completely gutted the place and I'm worried that whatever was up there travelled down to my place and is affecting my cat. Mario started scratching the same time all of this happened and like I said my cat has never been itchy like this before. Thanks again.

Have you tried eliminating grains and switching to canned food?

You said they gutted it probably made a lot of noise in doing so right? It could very while be the poor guy was completely stressed out by the noise. My dog ryder dosen't handle noise very while in 2013 my city decied to replace gas lines in the road then change the water lines on my street when they started getting close to my home he started digging and pulling his hair out he also had lost his bff around that time to. It was all from stress once they moved away from us and he had a chance to grieve his hair came back

You said they gutted it probably made a lot of noise in doing so right? It could very while be the poor guy was completely stressed out by the noise. My dog ryder dosen't handle noise very while in 2013 my city decied to replace gas lines in the road then change the water lines on my street when they started getting close to my home he started digging and pulling his hair out he also had lost his bff around that time to. It was all from stress once they moved away from us and he had a chance to grieve his hair came back