My daughter is having skin allergy probl

When my daughter is 2 year old she got red bumps on forehead and hands and legs and suffered with itching all the time.she suffered with it somamu months tried so many medications and it took nearly 10 months using various creams on her body to get her skin normal.they are itchy and red swallon looked likes musqueto bites.when the old ones disappear the new ones used to come.after that 10 months she never suffered like that again.now she is 6 year old n now she started getting those again a week ago she started to have small red bumps on forehead I observed that if she eats too much chocolates or sweet things she gets those red bumps.today suddenly she got those red swallon bumps all her hands and legs.why is this happening.what causes this skin problem.what care should be taken.she s saying they are very itchy