UVB and UVA rays can cause sunburn, brown spots, faster skin aging and increased risk of skin cancer. Obagi sunscreens help prevent sunburn and protect skin health because of their unique combination of ingredients: physical protection uses ingredients such as mineral pigments to reflect UV rays away from the skin and chemical protection uses chemical ingredients to absorb UV radiation and disperse it as heat. Sun Shield Matte SPF 50 will provide you with strongest sun protection available from Obagi, it absorbs quickly for a non-greasy, matte finish.