Cayenne pepper, derived from Capsicum annuum, contains the active compound capsaicin, which is responsible for its pungent heat. Its use for relieving sinus congestion has both traditional roots and emerging scientific support. Traditionally, cayenne and other hot peppers have been consumed to "clear the sinuses," likely owing to their ability to stimulate mucous membranes and promote drainage.

On the scientific front, several studies have investigated capsaicin's effects on nasal congestion. Capsaicin is known to activate transient receptor potential vanilloid 1 (TRPV1) receptors, which are involved in pain and heat sensation. When applied intranasally (via sprays or gels), capsaicin has been shown in clinical trials to reduce symptoms in patients with non-allergic rhinitis and chronic nasal congestion. The mechanism is thought to involve desensitization of sensory neurons and increased mucous flow, leading to temporary relief of congestion.

However, most studies utilize purified capsaicin preparations, not culinary cayenne pepper. The evidence for dietary cayenne (e.g., eating spicy foods) providing significant or lasting relief from sinus congestion is largely anecdotal, and effects tend to be short-lived. Side effects such as burning sensations or irritation are common, especially with direct nasal application.

In summary, while there is some scientific validation for capsaicin (the active component of cayenne pepper) in supporting relief from nasal congestion, the evidence is moderate (2/5) and primarily based on pharmaceutical-grade intranasal therapies, not dietary use.