Why does erysipelas cause spreading redness?

Erysipelas affects the upper layers of skin and the lymphatic channels close to them. The immune response increases blood flow and fluid in the tissue, producing a bright red, warm, swollen area that may have a raised, clearly defined edge. The border can enlarge as inflammation extends into adjoining skin. Chills, fever, tenderness, or feeling unwell may occur. A tiny break such as a cut, crack, bite, or sore can provide an entry point for bacteria.

Arrange prompt medical assessment for a red, hot, swollen area that is enlarging, especially when pain or fever is present. Marking the outer edge with a pen and noting the time can help show whether it is changing, but this should not delay care. Keep any wound clean, elevate an affected limb when comfortable, and take prescribed antibiotics exactly as directed.

Seek urgent help if redness is spreading quickly, fever or chills are strong, pain is severe, the skin becomes dusky or blistered, or you feel faint or confused. Emergency assessment is also needed when the face, area around the eye, or a large portion of a limb is involved. Worsening symptoms after treatment need review.

Ask what may have allowed bacteria to enter, how to take the prescribed treatment, which changes should prompt reassessment, and how to care for cracks, ulcers, eczema, or swelling that could raise the risk of another episode.