Which symptom is a hallmark of acute sinusitis?

A persistent headache is indeed a hallmark symptom of acute sinusitis. This condition is characterized by inflammation and swelling of the sinuses, which can lead to pressure and pain around the forehead, cheeks, and eyes. The headache typically worsens when bending over or lying down, as the changes in position can further affect sinus drainage.

In contrast, the other listed symptoms do not specifically relate to acute sinusitis. Chronic cough may occur but is not exclusive to this condition and can stem from various other respiratory issues. Excessive sweating is not a typical sign of sinusitis; instead, it is more commonly associated with systemic illnesses or fever. Increased thirst also does not connect directly with acute sinusitis and may indicate dehydration or other conditions not related to sinus inflammation. Thus, recognizing a persistent headache is crucial in the context of diagnosing acute sinusitis.