UV radiation damages hair as well as skin. The damage to hair can be treated the same way it can be for chemical processing but it cannot be reversed. There are many cosmetic formulations on the market claiming to help protect skin and hair from UV radiation. The best of these offer broad spectrum UV protection and on the label list an SPF. Sun protection products specifically for hair tend to offer and list UV filters and often to not have an SPF rating on the label. An SPF rating is regulated by government standards. The problem with an SPF skin product applied to hair is aesthetics. To get the proper amount of UV protection, one needs to use the product in the recommended required amount. That can make hair look less than desirable.
In 2011, the FDA instituted new SPF regulations. Health Canada has its own standards and is reviewing the FDA regulations. The European Union also has SPF regulations, as do other countries. What all of this means for the consumer is less confusion and better protection choices. Whether one chooses to buy all natural sun protection or conventional brands, regulations regarding SPF are now being improved.
I have read online that naturals oils, which include drying oils have been shown in research studies to have the equivalent of high SPF ratings. The research invariably concludes that these oils may prove to be valuable additions to sunscreen formulations. Natural products are subject to variations of potency because of factors that include: species; processing; crop year; handling, and storage. Unless such an oil has been tested and government approved and has an SPF rating on its label, there is no guarantee it offers such protection. Reputable vendors of such oils that I have seen that do not to have such labeling, are careful to point out that the oils "may" provide a sun protection factor, if added to a recipe. Then there are specifics involved for a formulation incorporating natural products and its potency that include: the solvents used to dissolve the oils and other natural products, the emulsions used, and the concentration and combinations of other ingredients. Unless such a formulation is SPF tested and approved, it is only speculation as to its actual if any, sun protection factor for the final result.
Sun protection clothing is available and that is regulated and tested separately to sunscreen formulations. There is very good information online regarding all of this and I have listed some references below.
What do I prefer? I am partial to the Ombrelle brand of sunscreens for my skin, and for my hair, while I have sun hats, I tend not to wear them. Instead, I have taken to using an umbrella for extra sun protection and to protect my hair, and this year I bought a Leighton Umbrella, UV protection 50+.