Fragrant oil (Latin name Santalum album) that can cause skin sensitivity, especially when used in pure concentrations. Sandalwood oil is a must to avoid if you have extra-sensitive skin or normally react to fragrance.
References for this information:
Indian Journal of Dermatology, January-February 2015, pages 3-12
Food and Chemical Toxicology, February 2008 pages 421-432
Encyclopedia of Common Natural Ingredients Used in Food, Drugs and Cosmetics, 2nd ed. New York, NY: John Wiley & Sons, 1996