It would be great if all it took to protect our hair from sun damage was sensibly formulated products with sunscreen. Redken (among many other lines) offers such products with all manner of protective claims, aside from an SPF number. This omission is intentional and in line with the FDA's protocol for sunscreen labeling. Since there is no way to know how much (if any) UV protection you're getting from hair-care products with sunscreen, the FDA does not allow such items to advertise an SPF number. We just don't know how long the sunscreen agents last, how they hold up during hairstyling and brushing, or how often they need to be reapplied to maintain the alleged level of protection. For the time being, your best defense to protect hair from sun damage (especially important if you bleach or highlight hair) is an opaque hat or scarf. I admit, such a look is not always the most practical, but if you're serious about keeping hair healthy, it's a workable solution when you'll be outdoors.
UV Rescue After-Sun Shampoo ($8.95 for 10.1 ounces) cannot rescue hair that has been damaged by the sun--no hair-care product can--because the manner in which sun damages hair is irreparable. Still, this is a respectable conditioning shampoo for all but fine or thin hair. The silicone will build up with time, but as long as you alternate this with a shampoo that does not contain conditioning agents, you'll be in the clear.
UV Rescue After-Sun Conditioner ($10.95 for 8.5 ounces) is a textbook definition of a basic conditioner: water, thickener, detangling agent, antistatic agent, and emollients. Nothing about this product holds any advantage for hair damaged by too much sun (you can't repair hair--it's dead), nor is this conditioner particularly soothing to the scalp, at least no more so than any other conditioner. However, just because it is basic doesn't mean it isn't effective. This conditioner works well for normal to dry hair of any thickness.
(Neutral Face) UV Rescue Blonde Guard ($12.95 for 5 ounces) is sold as a protective product to be applied to blonde hair before swimming. It is said to prevent discoloration from chlorine and other pool chemicals due to its water resistance. That claim is dubious, however, as chlorine doesn't discolor hair. Blonde hair can turn ashy green from the copper that leaches into pools from copper pipes. A plain silicone serum liberally applied to dry hair before swimming and a good, thorough shampoo afterward provide much more reliable protection. The UV claim is equally off base because without an SPF number it can't be substantiated.
UV Rescue Protective Oil ($12.95 for 5 ounces) is a nonaqueous silicone spray infused with gold-colored mica particles for a more dimensional shine. It contains sunscreen agents (including avobenzone), but is correctly not labeled with an SPF number. That didn't stop Redken from claiming this product "gives intense broadband UVA and UVB protection," which is a disingenuous statement when you consider that there is no SPF number. How much protection is present here--an SPF 2? Silicone can provide some heat protection during styling, but it cannot withstand the damaging effects of hours of sun exposure. Your best plan of defense to protect hair while in the sun is wearing a hat or scarf. Most people won't resort to those methods, however, which means some hair damage from sun exposure is inevitable.
Source: Paula Begoun