When you're out in the sun, you might only think about applying and reapplying sunscreen to the exposed areas of skin like the arms, legs, nose—you know the drill.

And that's a good practice to follow to an extent, but sometimes, you may need sunscreen under clothes. It's particularly important if you're wearing something that offers scant protection from the sun.

Less Protective Clothing

Garments that provide little if any sun protection typically include sheer items like beach cover-ups, but they can also include light-colored, wet, or loosely woven fabrics that are more transparent.

A good test is to hold it up to the sun and look through it. If you see a lot of light coming in, it's likely not an optimal choice for sun protection. Of course, that doesn't mean you can't wear it—you'll just need to apply and reapply sunscreen underneath as often as you do to the rest of your body.

Most Protective Clothing

Whereas sheer clothing offers the least protection, opaque, high-coverage garments like pants and long-sleeved shirts offer the most. That includes:

  • Dry, tightly woven fabrics that block rays from passing through such as high-quality synthetic materials, denim, or canvas
  • Shiny fabrics like polyester or satin, which can reflect radiation
  • Unbleached cotton, which contains organic polymers that help absorb the sun's rays before they reach your skin
  • Dark colors, which soak up the sunlight better than lighter shades

Just keep in mind that "tightly woven" doesn't mean "tightly worn." Generally, you'll want to keep your outdoor clothing loose-fitting, not only to keep you cool but also because when fabrics stretch out, the tiny fibers can separate and let in more light.

Clothes With Ultraviolet Protection Factor (UPF)

Some apparel is manufactured with a special coating that helps protect the skin from the sun's ultraviolet (UV) rays, whether they're wet or dry. These garments typically have a label that lists the UV protection factor (UPF). Some are even recommended by the Skin Cancer Foundation if they contain the organization's seal of approval.

UPF is kind of like the sun protection factor (SPF) of sunscreen, but it measures protection differently. While SPF indicates how well the sunscreen keeps the skin from burning during sunlight exposure, UPF tells you how much of the rays will pass through the fabric to the skin. A UPF 50 garment shields your skin from 98 percent of both UVA and UVB rays, which is good!

Other manufacturers sell chemical substances you can drop in the washing machine with your existing clothes to boost their protection power with a UPF layer. However, the American Cancer Society reports that there's not a lot of evidence that this DIY-style method works.

Keep in mind that even if you do wear thick or tightly woven fabrics, clothes can shift, hang, or ride up as you move. For this reason, it's smart to go a couple of inches beyond the boundary of your clothes when applying sunscreen. It could save you from an odd-looking tan line or a painful burn in a spot prone to chafing.

Don't Forget Accessories

As you pick protective clothing to wear day-to-day or when you travel, don't forget the accessories that will ensure you get the right coverage from head to toe:

  • Hats: Find a sunhat with at least a three-inch brim that covers your whole face while you're out and about. As with your clothing, it's best to choose a densely-woven material instead of straw, which can let in a lot of light. Also, look for options that have a dark color under the brim. The dark shade can help absorb UV light that reflects up off of water rather than it being redirected it to your face.
  • Sunglasses: Look for a label that indicates the level of protection from both UVA and UVB rays—99 to 100 percent protection is best. Wide frames can help shield sunlight from multiple directions.

You'll also want to pay attention to the quality of other accessories such as face masks, sandals, and gardening gloves. No matter what you wear, if it seems sheer, transparent, light-colored, or loosely woven, you should err on the side of caution and use an SPF product, too.

So, do you need sunscreen under clothing? Put simply, it's quite possible. However, it's even better to give your skin a healthy dose of moisture and SPF power with a UV broad-spectrum sunscreen that has an SPF of 30 or higher. It's a good option for the whole body and will ensure you have the right protection all over, no matter what layers you put on or take off throughout the day.