Clothing is a simple, effective sun protection tool that shades the skin from ultraviolet A (UVA), or long wave, and ultraviolet B (UVB), or short wave, rays. It provides a physical block that doesn't wash or wear off.
Long-sleeved shirts and pants, hats with broad brims and sunglasses are all effective forms of sun protective clothing.
Ultraviolet Protection Factor
The American Society for Testing and Materials has developed standards for the manufacture and labeling of sun protective products. The new units for UV protection are called ultraviolet protection factor (UPF).
UPF measures the ability of the fabric to block UV from passing through and reaching the skin.
- Good UV Protection — UPF 15–24
- Very Good UV protection — UPF 25–39
- Excellent UV Protection — UPF 40–50
Not all fabrics block UV light to the same extent. The UPF of clothing depends on several factors including weave and chemical additives when manufactured, (such as UV absorbers or UV diffusers).
UPF factors in order of importance are:
- WeaveTightly woven fabric provides greater protection than loosely woven clothing. If you can see light through a fabric, UV rays can get through.
- ColorDark colors provide more protection than light colors by preventing more UV rays from reaching your skin.
- WeightThe heavier the better. The weight of fabric is also called mass or cover factor.
- StretchClothing with less stretch generally has better UV protection.
- WetnessDry fabric is generally more protective than wet fabric.
For water sports, consider using UV protective swimwear, including rash guards and swimsuits. Some companies sell UV protective flotation devices and swim diapers.
Sunprotective clothing additives, such as Sunguard detergent, can be added to your laundry. Sunguard detergent is a UV blocking additive that when added to your laundry can transform clothing into sun protective gear with an SPF 30.
The active ingredient is Tinosorb FD, a UV protectant that can boost the SPF of a white cotton T-shirt from SPF 5 to SPF 30.
UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.
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Skin cancer is largely preventable, and if caught early, it's usually curable. It's important to take precautions when spending time outdoors. Learn more.
Dermatology Clinic at Mount Zion
1701 Divisadero St., Third and Fourth Floors
San Francisco, CA 94115
High-Risk Skin Cancer Clinic
1701 Divisadero St., Third Floor
San Francisco, CA 94143-0316
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Bakar Precision Cancer Medicine Building
1825 Fourth Street, Third Floor
San Francisco, CA 94158