Citrus fruit that’s a potent skin sensitizer.The juice from lemon is often touted as being a natural option for brightening skin. The truth is that lemon juice is highly acidic (has a very low pH of 2) and exceedingly sensitizing to skin. Lemon juice applied to skin can cause photosensitivty on exposure to sunlight, which is due to a volatile fragrance chemical known as limonene, which is abundant in lemon juice. Lemon, whether in juice or oil form, is a must to avoid in cosmetics.
Reference for this infomation:
Journal of American Academy of Dermatology, 2002, issue 5, pages 709-714