Benefits of Sun Protective Clothing

Making sense of sun protective clothing: What is the UPF?

Erum N. Ilyas, MD, MBE, FAAD

 There is a lot of talk about sun protective clothing. Many of my patients ask, “doesn’t all clothing protect against the sun?!” This is a very reasonable question given the fact that, yes, there is physically something between your skin and the sun. The real question is how much protection does clothing actually provide.

Most people are familiar with the SPF (sun protection factor) of a product when finding sunscreens. The sun protection of clothing is measured by a different scale called the UPF. UPF stands for ultraviolet protection factor. The UPF is a measure of how much protection a fabric or textile protects against the sun. One of the ways that UPF differs from SPF is that UPF measures both UVA and UVB protection, whereas the SPF only measures UVB protection.

The ability of a textile to block UV light is influenced by its weave, color, and weight amongst some other factors. In general, the tighter the weave, the darker the color, the heavier the material, and the more elastic the fabric the more likely the textile will provide adequate UV protection. Most often, the UPF is based on the textile itself and not by sunscreen additives embedded in the fabric. The UPF measurement indicates how much UV is absorbed by the textile. For example, a UPF of 15 means that 15 units of UV is blocked by the textile while 1 unit of UV passes through the fabric to reach the skin.

 

UPF Rating Category % UV Radiation Blocked
15 – 24 Good 93.3 – 95.9%
25 – 39 Very Good 96.0 – 97.4%
40 – 50+ Excellent 97.5 – 98+

 

This brings us back to the initial question- “doesn’t all clothing protect against the sun?”. The answer is yes, but not all clothing is the same. The UPF of many summer fabrics such as linen and cotton depending on how tight the weave, as well as summer colors such as white and pale colors puts the UPF of a thin white T shirt closer to a 5! This means that over 20% of UV radiation will reach your skin. It’s also important to take into consideration the fact that repetitive washing of clothing does tend to lower the UPF by loosening the weave.

Take a look at these pictures to see the difference…

Montgomery Dermatology

50x magnification. Textile with UPF 50+ (left) and Standard white T Shirt (right). | Photos courtesy of Erum Ilyas, MD

Next time I will discuss different textiles in more detail and how effectively they block UV light. Since not all clothing specifies a UPF factor, knowing this will help make smart choices when shopping!

Erum N. Ilyas, MD, MBE, FAAD

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