Extract derived from the plant commonly known as pot marigold or Calendula officinalis, there is little research showing that it has any effect on skin, though it may have antibacterial, anti-inflammatory, and antioxidant properties. If you have ragweed (or similar plant) allergies, topical application of calendula is not recommended because of the risk of an eczematous allergic reaction. 
- Reider N, Komericki P, Hausen B, Fritsch P, Aberer W. The seamy side of natural medicines: contact sensitization to arnica (Arnica montana L.) and marigold (Calendula officinalis L.). Contact Dermatitis. 2001;45(5):269-72.