Does Clothing Protect You From the Sun?
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I recently went to the dermatologist for my annual mole check-up.
"Do you wear sunscreen?" He asked.
"No" I said, "but since I am outside a lot, I try to always wear a long sleeve shirt, work gloves and a wide brim hat."
Can you guess the level of SPF protection my dermatologist said I get from wearing a normal cotton shirt?
My dermatologist informed me that a regular cotton shirt gives covered skin the equivalent of a disappointing SPF 7 protection against UV rays! Blue denim jeans, on the other hand, can provide SPF 166 protection or higher! (To give those numbers a reference, the American Academy of Dermatology recommends SPF protection of at least 30.)
Note: Technically, the sunburn protection of clothing is measured on the UPF (Ultraviolet Protection Factor) rating scale while sunscreen protection is measured with SPF (Sun Protection Factor) scores. The 2 measurement methods, however, are roughly comparable for our purposes here.(8)
It turns out that claiming a t-shirt provides SPF 7 protection may actually be overly generous.
There are many factors that influence a garment's UV blocking capability. In some cases, my t-shirt may provide closer to SPF 3 or 4 protection(4). The factors include:
- material: polyester may be more effective than cotton since it reflects rather than absorbs UV rays.
- fit: looser is better.
- weave and color: typical white t-shirt can have an SPF value as low as SPF 4 while heavy blue denim might provide protection as high as SPF 166.(1)
- condition: stretched and wet garments compromise a garment's UV protective ability!
My dermatologist strongly suggested that I consider:
- wearing special UV-protective clothing (2)
- applying broad-spectrum protection, SPF 30 or greater, water resistant sunscreen. This is especially important for protecting uncovered skin but sunscreen can be certainly applied under those light weight or light color garments.
What is the SPF of clothing? (A general rule of thumb)
Unfortunately, the heavier and darker the garment, the better the UV sun protection: "All clothing offers some degree of protection. When the sun's rays hit fabric, some of the energy is changed to heat. This converted energy is no longer dangerous to skin."(1)
The good news is that special UV protective clothing is able to halt the sun's damaging rays, yet it is comfortable and breathable... even on sunny, hot days.(2) The fabric is so tightly woven that it prevents UV radiation from penetrating to reach your skin... or the fabric may be treated with UV blocking ingredients like zinc oxide. In fact, it can be argued that UV protection clothing is even more effective than topical sunscreen. That's because sunscreen is often used improperly(3):
- sunscreen with SPF 30 or higher should be applied 30 minutes before exposure so it can be absorbed. It also must be reapplied every two hours and immediately after swimming, sweating, or toweling off.
- Sunscreen is often applied too thinly. Each application should consist of a 1 ounce (enough to fill a shot glass) to the entire body. After reapplications, expect a family of four to use a full four-ounce bottle of sunscreen during a long day outdoors.
- Areas of exposed skin might be missed.
Does UV protection wash out of clothing?
No! The sun blocking qualities of UV protective clothing never washes out. However, the garments fabric will wear and weaken over time... just as with any other fabric. And this can decrease the UV protective qualities of UV protective garments.(9)
A 2019 article published in JAMA looked at the possibility of sunscreen chemicals being absorbed into the body and the potential health risks of those chemicals.
"The study examined four common sunscreen components: avobenzone, oxybenzone, octocrylene and ecamsule. For all four, systemic concentrations passed the nanogram threshold after the applications on the first day of the study. The levels were higher than the limit for the entire week for all the products except the cream."
"They also increased from Day 1 to Day 4, meaning that there was accumulation of the chemical in the body with continued use."(3)
So, what was the sunscreen recommendation that came out of this study?
Since UV damage to the skin is irrefutable, continue using sunscreen! To play it extra safe, however, consider switching to sunscreens that contain zinc oxide and titanium dioxide.
These inorganic compounds are not absorbed into the body, and sit on the skin reflecting or absorbing the sun’s harmful rays.
Note: there is a slight tradeoff to using zinc oxide and titanium dioxide: "Because they aren't absorbed, they’re also noticeable. Most people prefer sunscreens that are absorbed." Also, they take a bit more effort to apply since "lots of parents in particular prefer sprays because they’re easier and faster."(3)
Final Thoughts on UV Protection: Lips and Eyes
Don't forget to protect your lips and eyes! Lip cancer is causally related to lifetime sun exposure and UV rays account for about half of all lip cancers.(5) And long term sun exposure may contribute to severe eye problems later in life, such as macular degeneration and cataracts.(9)