Aster root (from various species within the Aster genus) has a long history of traditional use in herbal medicine, especially within Chinese and Native American herbal practices. In Traditional Chinese Medicine (TCM), the root of Aster tataricus (commonly called Zi Wan) has been used for centuries to support respiratory health, including conditions involving coughs, phlegm, and congestion. These traditional uses sometimes overlap with what Western herbalists would call "sinus support," as the herb is thought to help clear mucus and ease breathing.

However, there is limited scientific research specifically validating aster root's effectiveness for sinus support. Most available studies focus on its general expectorant, anti-inflammatory, or antimicrobial properties, which could hypothetically benefit the upper respiratory tract, including the sinuses. Animal and in vitro studies suggest some anti-inflammatory and immune-modulating effects, but rigorous clinical trials in humans are lacking.

Therefore, while aster root's use for sinus health is primarily justified by tradition and historical application, there is insufficient modern scientific evidence to strongly support its efficacy for this purpose. Its rating reflects traditional use with limited scientific backing.