Calendula has anti-inflammatory, antioxidant and antimicrobial properties. 
 
Here are just a few clinical studies....
A clinical study was done and observed people with gingivitis witnessed calendula mouthwash significantly reduced their dental plaque and inflammation in the gums. 
Another clinical study looked at patients with head and neck cancers and found that calendula extract decreased the intensity of radiotherapy by reducing free radical activity. This research indicates that calendula has antioxidant activity. 
In an animal study, researchers noticed that calendula extract has liver-protecting effects because it decreased oxidative stress and prevented free radical activity. 
Calendula has the ability to stimulate and cleanse the lymphatic system.
Calendula may help support the immune system and digestion.