My dog and a rash?

I've seen a lot of red skin and blotches on my dogs neck. It doesn't seem to bother her but it looks really red, and possibly has a small amount of puss. I don't know what it is can anybody help me?|||Have you put anything on the dog, like flea treatment or a flea collar? Dog's don't really express their discomfort until it is really bad so you should get it looked at by a vet even though it doesn't seem to be bothering the dog. Without seeing it, my first thought is an allergic reaction or mange, but it could be a lot of things.|||Probably an allergic reaction, have you changed food or collars or taken her some place new, has a bug bit her? If there is pus it is infected, VERY dangerous, especially around the neck. better get her to the vet.|||Might be mange or lyme disease. Get your dog to a vet straightaway.|||Take her to the vet. It might just be an allergy, but get it checked out ASAP