What we haven't talked about is how to protect your. . . uh, personal areas while you're spending time in a tanning bed.
Why? Well, apparently, over-exposure to UV rays can actually cause sterility. And because the tip of the male penis is actually mucosal membrane, like human eyelids, and not the same kind of skin as the back of your hand, it can actually become discolored or disfigured if it's damaged.
Similarly, the eyelids, nostrils, lips, and inner ear do not contain pigment, and are not meant to hold color, so it's important to keep them protected. You can apply SPF lotions and lip balms to the appropriate areas, but what should you do about other areas that you just shouldn't apply lotion to?
There are commercial products available to cover a man's penis or a woman's nipples, or you can just use a piece of nylon/lycra. Cotton actually only blocks 6 - 9% of UV rays, which means you can still get burned.
It's also important for women who have chemically-treated hair to keep their hair covered while they're tanning, because your hair can actually change color inside the tanning bed.
While I have yet to meet anyone who has suffered from any of these ailments as a result of nude tanning, the mental image of discoloration is enough to send almost anyone running to cover up with these types of products.