Unless your clothing specifically states sun-protective, don’t rely on clothing alone. Clothing has a its own protection factor: the Ultraviolet Protection Factor (UPF). As with SPF, the higher the UPF, the better the protection.
The UPF rating indicates how much the fabric reduces the skin’s UV radiation exposure. For example: UPF 20 allows only 1/20th of the sun’s UV radiation to pass through it.
A garment cannot be labeled “sun-protective” or “UV-protective” if its UPF is less than 15.
Sun-protective clothing may lose its effectiveness if it’s too tight or stretched out, damp or wet, or if it has been washed or worn repeatedly.
Sun-protective fabrics typically have a tighter weave or knit and are usually darker in color.
Unless your clothing is specifically labeled UPF 15 or higher, you cannot safely assume that it can protect your skin from UV light. However, any clothing (longer sleeves, hats) can add to your protection. Just make sure you’re not relying on clothing alone—don’t forego the sunscreen.
Note: applying sunscreen naked, under your bathing suit, prevents missing a spot. But sunscreen under thicker clothing may be too hot for some, especially young children, and result in overheating or rashes. To be sure, ask your doctor about your sunscreen.