If you read any sunscreen directions, it always says, "Apply a generous amount" or "Apply liberally." Exactly what does that mean? The BIGGEST confusion that I hear from my patients is in knowing exactly HOW MUCH sun screen to apply.
Let me show you how much. 1 oz of sunscreen being needed for covering the body of an adult. That is the amount to fill a shot glass. Few people actually use this much sunscreen.
Most people do not apply a thick enough amount of sunscreen and therefore are not getting the promised SPF protection.
You need to use this amount again when you reapply the sunscreen every 2-2.5 hours.
I brought with me some photoprotective clothing, specifically, swimshirts. You can also get photoprotective gardening shirts, golf shirts, you name it. But I use this type of shirt when going to the pool or beach.
The most important difference between this clothing and a normal T-shirt is the weave or knit - the tighter the knit, the less ultraviolet light that gets to your skin to cause a burn. An easy way to demonstrate this to yourself is to hold up your T-shirt to a light bulb or the sun and look at how much light is streaming through the fabric. That is light that gets to your skin.
The typical T-shirt has an SPF of between 4 and 7, and when it gets wet, it can go down even lower. These shirts have an SPF approaching anywhere from 35-50 and they keep it while wet.
The other important difference is in the design of the shirt. Notice the high neck collar to help protect more skin. T-shirts obviously do not have this.
Finally, T-shirts are heavy to swim in, while these shirts feel weightless in water and dry almost instantly.