Which is a known symptom of measles?

The correct choice, a red, blotchy skin rash, is characteristic of measles and typically appears 3 to 5 days after the onset of fever and other initial symptoms such as cough, runny nose, and conjunctivitis. This rash usually begins on the face and neck before spreading to the rest of the body and is often described as maculopapular in nature, meaning it consists of flat, red spots that can merge together.

The other options do describe skin conditions but are not associated with measles. An itchy rash is more commonly linked with conditions like allergic reactions or eczema rather than measles, while a blistering rash is associated with infections such as chickenpox. White patches in the mouth, known as Koplik spots, can occur with measles but are a specific finding within the oral cavity rather than a skin symptom. Hence, the classic presentation of a red, blotchy skin rash aligns with the well-known clinical manifestations of measles.