Citrus Oils Caution
Photosensitizing: Some essential oils (typically citrus oils) contain natural substances called furanocoumarins. Furanocoumarins can react with ultraviolet light to create substances that may cause hyperpigmentation or burning on the skin. While essential with furanocoumarins have many beneficial properties, care should be taken after applying these oils on the skin to protect the skin from direct, prolonged ultraviolet light exposure for 1–3 days.(Modern Essentials, 6th Edition, inside front cover)
I recommend that you check NAHA (National Association for Holistic Aromatherapy) for safety information about essential oils.