Cellulitis is a bacterial skin infection that commonly occurs on the lower extremities—including the feet, which are prone to edema (swelling) in people with poor foot circulation, like diabetics and those who are sedentary. Common bacterial causes of cellulitis are group A streptococcus, streptococcus pneumonae and staphylococcus aureus bacteria, according to the University of Virginia. Foot injuries such as a heel crack or athlete's foot often serve as entry portals for bacteria, podiatrist Marc Mitnick explains. Symptoms of cellulitis on the foot can worsen rapidly and need medical attention.
Cellulitis on the foot causes redness and swelling. Redness may spread up the leg if the bacteria travel through the bloodstream; red streaks going toward the heart are also a sign of spreading infection. If the foot feels hot to the touch or if skin on the foot is reddened, blistered or has a slightly pitted (orange peel) appearance, the Merck Manual states, you may have cellulitis. Small red dots known as petechiae may be seen on top of the reddened area. If the foot turns black, serious damage to the tissue may be occurring, and immediate medical attention should be sought.
Cellulitis can cause severe pain, especially in dependent areas like the foot, where extra fluid accumulates easily from swelling. Walking can be painful, and the skin may be tender to touch. In addition, lymph nodes in the leg may become tender to touch if the infection spreads; and repeated cellulitis infections in the foot can permanently damage the lymph nodes in the leg. Elevating the foot reduces pain and decreases swelling.
Fever is a common accompaniment of cellulitis, as the body attempts to fight off the bacterial invaders. If cellulitis is worsening or spreading from the foot up the leg, chills can occur with fever. In some cases, people with cellulitis have a fast heart rate, known as tachycardia, and feel lethargic. Headache and confusion may also occur.