Widely-used plant that's a member of the mint family. It is primarily a fragrance ingredient, although it may have antibacterial properties. There is no research showing it has any benefit for skin (Sources: Phytotherapy Research, June 2002, pages 301–308). In fact, it can be a skin irritant but there is a conflicting research on just how much of a photosensitizer lavender can be. It appears lavender oil all by itself isn't a photosensitizer, but when exposed to oxygen (as it would be when applied to your skin), one of it's fragrant components, linalyl acetate forms substances that lead to allergic contact dermatitis in and out of sunlight (Sources: The New Ideal in Skin Health: Separating Fact from Fiction, Thornfeldt, Carl M.D., Allured Books, 2010, pages 286–287; Contact Dermatitis, January 2008, pages 9–14; Hautarzt, February 2002, pages 93–97; and Contact Dermatitis, August 1999, page 111).
Research also indicates that other components of lavender, specifically linalool, can be cytotoxic, meaning that topical application causes skin-cell death (Source: Cell Proliferation, June 2004, pages 221–229). Lavender leaves contain camphor, which is known as a skin irritant. Because the fragrance constituents in lavender oil oxidize when exposed to air, lavender oil pro-oxidant. This enhanced oxidation also increases its irritancy on skin (Source: Contact Dermatitis, September 2008, pages 143–150). Lavender oil is the most potent form, and even small amounts of it (0.25% or less) can be problematic. It is a must to avoid in skin-care products, but is fine used as an aromatherapy agent for inhalation or relaxation (Source: Psychiatry Research, February 2007, pages 89–96; and www.naturaldatabase.com).