Which of the following is NOT a symptom of infection?

The presence of clear skin indicates a lack of infection, as it suggests that there are no visible signs of inflammation or disease commonly associated with infection, such as redness, pus, or lesions. In the context of symptoms, fever, swelling, and cough are all typical indicators that an infection may be present.

Fever often occurs as the body's response to fighting off pathogens, indicating that the immune system is actively working against an infection. Swelling may result from inflammation in response to an infection, as the body's tissues can become inflamed when responding to foreign invaders. A cough can also be a symptom of respiratory infections, signaling irritation or inflammation in the airways.

In contrast, clear skin signifies the absence of such underlying processes associated with infection, making it the choice that does not align with typical infectious symptoms.