How fo uou know when you have cellulitus?

Swelling, pain, etc: Usually cellulitis presents as increased pain in the area, redness and swelling. It usually has a "sore' as the starting point and spreading redness and swelling.

Pain, redness: U will notice redness, pain, swelling and area would feel warmer than other areas.

Red, pain: Skin infection-- redness, tender, may extend without treatment, may be associated with swelling, fever.