How can one treat cellulitis if it does not heal?

Cellulitis. Cellulitis is a bacterial infection of the skin. It's superficial and treatable with antibiotics, either topical or oral. Some infections can be very severe and possibly deadly (MRSA), so don't take cellulitis lightly. See a doctor if you have symptoms of redness, warmth and tenderness of an area of your skin, especially if you have fever, chills or sweats.
What's the cause? Cellulitis is basically a visible inflammation (itis) of the skin and soft tissues (red, hot, swollen and tender). It can be caused by many things including sunburn (radiation), trauma (sprained ankle) or poor vein circulation (stasis dermatitis). It need not be caused by bacteria. If you have repeated episodes of this, get to a wound care or vascular specialist, the diagnoses you have is wrong.
Depends on cause. There are some forms of cellulitis due to vascular deficiency. Massive obesity can be a deterrent to effective healing. The nature of the organism is important in selecting antibiotics. But in the long run it may just be slow resolution of symptomatic expression and healing of tissues rather than continuing disease.
See below. For the most part, with the right treatment plan cellulitis will heal. On occasions one may have to amputate a digit or limb to cure cellulitis.