A water-soluble, chemical sunscreen agent that is a secondary UVB absorber with some activity in the short UVA range as well. Being a secondary UV absorber means that its protection is weak and it has to be combined with other sunscreen filters for proper sun protection.
More often than not, Benzophenone-4 is not used as a sunscreen agent but as a photoprotectant to extend product shelf life, or as a color-protectant for products in clear packages.
A Contact Dermatitis article from 2007 names BP-4 as an emerging allergen, as it was the most frequently positive chemical UV filter and third most frequently positive ingredient overall among the 35 substances patch tested in the study (13 positives of 1693 people tested).
Show me some proof
- Hughes, T. Merion, and Natalie M. Stone. "Benzophenone 4: an emerging allergen in cosmetics and toiletries?." Contact dermatitis 56.3 (2007): 153-156.