The skin is very red, hot, and sore to the touch. Cellulitis is caused by a variety of germs but usually Staphylococcus, Streptococcus, or Haemophilus influenzae.
Antibiotics are definitely in order.
Especially dangerous is cellulitis arising from infected chickenpox , caused by the Group A streptococcus bacterium. Whenever you suspect a cellulitis is developing, and especially in cases of chickenpox, call your doctor . Avoid ibuprofen for fever if you suspect cellulitis, especially with chickenpox. It is suspected to cause suppression of the normal inflammatory response to cellulitis with dangerous delay in diagnosis.