hen I was 12 years old I made the momentous decision to start shaving my legs. Although I had been thinking about this for months, I was hesitant. Everyone seemed to know that if you started to shave, your hair would grow back thicker, and there was no going back. As it turned out, I didn't mind shaving so much, and apart from the occasional cuts, it didn't cause me many problems. So, it never occurred to me to question the idea that shaving was a lifetime endeavor until I started to learn a lot more about skin during my dermatology residency.

During that time I quickly learned that much of what you "know" about your skin is dead wrong. I now frequently spend time with my patients outlining basic skin care principles and explaining why some of their beliefs about skin don't stand up to proof. Think you know more than my average patient? See if you can tell myth from reality in the following statements: Pick the one that you think is true, then read on to find out if you were right, and maybe learn a thing or two.

Junk food causes acne.
If this were true, it would certainly be motivation to improve your diet, but it just isn't so. A recent look at data from the Nurses Health Study (a large and well run epidemiological trial) suggested a link between increased milk intake and worse acne in teenagers. But the same study found no association between intake of soda, chocolate candy or pizza and worsened acne. Not that I recommend eating lots of junk food -- I don't, but I just can't say avoiding it will improve your skin. So, what can help acne? There are several medically proven treatments, including some available over the counter. These include benzoyl peroxide treatments (cleansers like PanOxyl or wipe pads like Stridex Power Pads) and salicylic acid products (such as Clarity cleanser by Olay or Neutrogena On the Spot treatment).

Shaving makes your hair grow in thicker.
In fact, shaving doesn't make your hair thicker, nor make it grow faster. When you shave you remove the thin tapered tip of the hair and leave only the thicker middle portion protruding from the skin surface, so your hair may feel a little thicker. But with enough time, your hair will grow longer, and feel thinner and softer again. Of course, many people don't want to give it the time to grow back, so they just keep shaving once they start. Shaving can cause ingrown hairs. The best way to extract them is with a laser treatment.

vitamin E is good for scars.
My patients frequently tell me that they have heard that vitamin E will make their scars heal better. In fact, vitamin E can be irritating to the skin, and even produce allergic reactions. In one study of patients with burns, vitamin E made some scars look worse. Instead of vitamin E, clean a burn or wound daily with a mild cleanser or soap and water, followed by a soothing cream such as Aquaphor Healing Ointment. For scars that become raised and firm, treatments such as steroid injections can be helpful. For persistent redness in scars, try a laser treatment

Only daily sun exposure can insure adequate vitamin D levels.
This is not only false, it is also potentially dangerous. Even with sunscreen, most people get more than enough sun on a daily basis to keep vitamin D levels sufficient. In fact, most people can get all the vitamin D they need from diet or from vitamin supplements without any sun exposure at all. It is true, however, that excessive sun exposure can lead to an increased risk for skin cancer. Apply sunscreen daily, SPF 30 or higher, and never sunbathe.

People who tan easily don't need to worry about sun exposure.
People who tan easily are less likely to burn from sun exposure, but they're still at risk for skin cancer if they get too much sun. Furthermore, skin that tans easily can also suffer other damaging effects, including increased wrinkling and uneven pigmentation. In my book it just isn't worth the risk. If you absolutely must have that color, try a self-tanner. These are generally safe and can produce a pretty good approximation of a tan without the added risk of skin cancer. Take your pick of products, including Clarins Instant Self-Tanning Gel, Neutrogena Instant Bronze and Coppertone Endless Summer.