There are many factors to consider when selecting a sunscreen, and it’s important to have an understanding of what impact they each have on the effectiveness of UV protection they provide.
Broadly speaking, there are two different ways sunscreens protect against UV radiation; chemical protection and physical protection. Chemical sunscreens introduce materials into the skin that absorb UV radiation, while physical sunscreens (like zinc cream) create a physical layer of protection that reflects or blocks UV radiation.
Newer sunscreens contain elements of both. They are able to provide both physical and chemical protection, without the visible white layer that zinc oxide (physical) has provided in the past. This is achieved by introducing nanoparticles of zinc oxide or titanium dioxide into a chemical sunscreen, as the zinc and titanium dioxide both retain the UV protective capabilities present in their coarser form.
There has recently been some concern over the use of these nanoparticles in sunscreens. Studies to date have shown no relationship between the presence of these particles and any significant increased risk or side effects, but regulatory agencies are continuing to monitor and carry out research.
While SPF rating can provide a good indication, and at the moment is the only universally accepted method of rating sunscreen, it must be remembered that SPF ratings refer only to the level of protection provided from UVB radiation. As a general rule, the higher the SPF, the better, as this protects against UVB radiation.
‘Broad spectrum’ is a term indicating that a sunscreen is effective in protection against UVA and UVB radiation and should be a compulsory feature of any sunscreen selection.
Many sunscreens promote themselves as water-proof, or water resistant. Typically, water-proof sunscreens will last for 80 minutes in the water, while water resistant ones will endure for 40 minutes. The choice here is dependent upon the sort of activity the individual is likely to engage in.
Essentially, the decision should come down to these requirements:
- Broad spectrum
- SPF 30+ or greater (if available)
- Chemical versus physical protection (or both)
Beyond that, it’s most important to remember to apply sunscreen and apply it properly, as we will discuss in the next post.
References:
http://www.tga.gov.au/npmeds/sunscreen-zotd.htm
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