Cayenne pepper (Capsicum annuum), which contains the active compound capsaicin, is used to support sinus health, particularly for its effects on nasal congestion. Scientific research provides some validation for this traditional use. Capsaicin has been studied for its ability to relieve symptoms of non-allergic rhinitis and chronic sinusitis. Mechanistically, capsaicin works by desensitizing sensory neurons and inhibiting the secretion of substances that contribute to inflammation and mucus production in the nasal passages.

Several clinical trials have shown that intranasal capsaicin sprays can reduce nasal congestion and improve sinus symptoms, especially in patients with non-allergic rhinitis. For example, a randomized, placebo-controlled study published in "Annals of Allergy, Asthma & Immunology" (2011) found significant symptom improvement with capsaicin treatment compared to placebo. However, most of these studies use purified capsaicin in a nasal spray rather than dietary cayenne pepper, so the effectiveness of consuming cayenne pepper for sinus issues is less well established.

In summary, there is moderate scientific evidence supporting the use of capsaicin (the main active compound in cayenne pepper) for sinus support, especially when applied locally. The evidence does not strongly support the use of dietary cayenne pepper for sinus health, but its mechanism and clinical research on capsaicin suggest a potential benefit.