Updated May 31, 2014.

Ultraviolet rays from the sun consist of UVA, UVB and UVC rays.  Longer-wave UVA rays are predominantly responsible for premature skin aging, causing changes in pigmentation, thickening of the skin and coarse texture, large pores, and in some cases aggravating adult acne. Both UVA and UVB rays contribute to skin cancer, the world's most common form of the disease.

UVA rays are able to pass through glass, meaning you are still vulnerable to skin damage indoors, while driving or working near a window.;

The best protection against damaging UVA rays is a sunscreen which offers broad-spectrum coverage, meaning it blocks out both UVA and UVB rays.

Read more: How does the sun cause premature aging?

<sub>Source:

Siddharth Mukherjee, Abhijit Date, Vandana Patravale, Hans Christian Korting, Alexander Roeder, and Günther Weindl. "Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety." Clin Interv Aging. 2006 December; 1(4): 327–348.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699641/

Sunscreen FAQs. American Academy of Dermatology Public Information Sheet. Accessed May 30, 2014.
http://www.aad.org/media-resources/stats-and-facts/prevention-and-care/sunscreens</sub>