Photosensitivity

Photosensitive oils.  Look to oils which contain furanocoumarins.
http://suite101.com/article/photo-toxic-essential-oils-a69964
http://www.naha.org/articles/brief_safety%20guidance%20.htm

Essential oils of verbena, mandarin leaf, bergamot fruit, lime fruit, bitter orange fruit, lemon fruit, grapefruit, cumin seeds and angelica root. 

Not patchouli, not celery, not cedarwood, not mandarin fruit, not tangerine fruit, not bergamot FCF, and not parsley. 

So not all citrus oils are photosensitive, Mandarin and Tangerine stand out.

Ian Brealey