This is a condition also known as Puppy Head Gland Disease, Juvenile Pyoderma and Juvenile Cellulitis. It affects puppies of a few weeks old and can occur in any breed although some seem more prone than others. It is immune-based and starts as pimples of infection around the face and muzzle although it can also start just as swellings in the neck.
The most common bacteria isolated is Staphylococcus intermedius but often nothing is isolated from samples taken. This rapidly progresses to swelling around the muzzle and head which can be extensive. Most puppies also have a high temperature, are lethargic and some can get secondary septicemia leading to joints being affected as well. Some may have other issues such as Demodectic mange or Scabies but often there is nothing found.
The most effective treatment is immunosuppression using steroids such as prednisolone (antibiotics are given to combat the often weepy skin but on their own do not resolve the problem).
The condition will usually completely resolve in a couple of weeks or so usually never recur. Sometimes whole litters can be affected but often-just one or two and the others although siblings may nip them do not develop the extreme swelling and discomfort.