Fragrant substance that, because of its resin and volatile oil content containing monoterpenes can be extremely sensitizing on abraded skin. There is no research showing it has any benefit on skin, though it has natural, short-term (6 months) preservative qualities in emulsions.
References for this information:
Journal of Agricultural and Food Chemistry, February 2009, pages 1,433-1,439
Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics. 2nd ed. New York, NY: John Wiley & Sons, 1996
Biological and Pharmaceutical Bulletin, September 1993, pages 912-916