Which physical exam finding is indicative of cellulitis?

Erythema and edema are classic signs that indicate the presence of cellulitis, which is a bacterial skin infection characterized by inflammation of the skin and subcutaneous tissues. The redness (erythema) occurs due to increased blood flow to the affected area as the body responds to the infection, while edema is the swelling resulting from the accumulation of fluid and immune cells in the tissues. These signs help differentiate cellulitis from other conditions affecting the skin, as they reflect an active inflammatory process associated with infection.

In contrast, the other choices represent findings that either do not align with the typical presentation of cellulitis or suggest alternative diagnoses. Coldness on palpation may indicate reduced blood flow or vascular compromise, which is not characteristic of cellulitis. Lack of sensation can imply nerve involvement or damage but is not a defining characteristic of cellulitis. Localized swelling without discoloration could suggest other issues, such as trauma or a non-infectious process, rather than the clear signs of infection seen in cellulitis. Thus, the presence of erythema and edema is the most reliable indicator pointing to this condition.