As the days get longer and the weather heats up, many people's minds turn to skin -- perhaps because they plan to show more of it in the coming months.
With that in mind, we approached a number of myths about how to help your skin look its best. Some of these are warnings you heard from your mother, while others are the type you might have heard from your friend who subscribes to 20 magazines. Some are proverbial old wives' tales, others have solid medical evidence behind them, and a few are true -- but misleading.
Does shaving really make your hair grow back thicker? Can squinting give you wrinkles? Will dry brushing really help you get rid of your cellulite? Does getting a base tan in a salon help you avoid sunburn?
These myths have taken hold as standard advice on skin care. But do they stand up to the scrutiny of dermatologists?
Fact or Myth? Shaving makes hair grow back thicker.
"That's definitely a myth," said Dr. Arielle Kauvar, a clinical associate professor in NYU's department of dermatology.
But there's a reason why shaving might appear to have that result.
"When you shave, you're seeing the blunt edges of the hair regrow all at the same time, so there's an appearance of being thicker, but there's no difference in the diameter or the density of the hair," Kauvar said.
Hair doesn't seem to grow in as thick in waxing, because the entire follicle is removed, so the hair coming back in is growing in different cycles. As a result, it does not appear to be as dense. Also, the hair is tapered at the end, so it does not appear to be as thick.
Fact or Myth? Exfoliating can slow hair growth.
Doing something to your skin doesn't seem to affect something that grows below it.
"Exfoliating the surface of the skin -- it's not going to change the metabolism of the follicle underneath the skin," said Dr. Ronald Brancaccio, director of the Skin Institute of New York.
The only current treatment available to slow hair growth is the drug Vaniqa, which is applied topically to reduce facial hair growth in women. It works by blocking an enzyme that enables hair follicles to grow.
A number of illnesses can also lead to a temporary loss of hair. These include thyroid problems and a condition known as telogen effluvium.
Typically, 20 percent of hair is in the resting phase -- where it is not growing -- at any given time. Illness, trauma or childbirth can lead to telogen effluvium, where a greater percentage of the hair is pushed into that resting phase, making it seem like hair fell out overnight.
Fact or Myth? All wrinkles form by age 25 -- they just start to show later.
This is known to be a myth largely because activities after 25 -- like spending more time out in the sun -- can lead to an increase in wrinkles.
"If you get a lot of sun exposure, you're definitely going to get more wrinkles," said Dr. Zoe Draelos, a dermatologist in private practice and a researcher in High Point, N.C.
Wrinkles are the result of a loss of collagen, the main structural protein of the skin. As you age, the body begins to produce less of it, which keeps skin from being as firm as it was when you were younger.
But while that decline in collagen happens to everyone, and wrinkles will form along the lines that are moved in facial expressions, sun exposure breaks down collagen even more, leading to wrinkles that otherwise might never have happened.
Fact or Myth: Squinting or rubbing your eyes and face can cause wrinkles.
Wrinkles occur where they do because of the places where skin cells are squeezed millions of times by facial expressions.
As the skin loses firmness with age, wrinkles form where it has been squeezed.
So, squinting, or any other repeated facial expression, like frowning or smiling, will lead to wrinkles when it is done enough times.
But, while facial expressions may be the cause of wrinkles, there's little that can be realistically done to prevent them from forming.
"You can't walk around stone-faced all day," Brancaccio said.
The appearance of wrinkles can be improved with Botox, which is injected in the forehead, between the eyes, to keep the muscles from moving.
Rubbing your eyes, on the other hand, is highly unlikely to leave marks.
"Rubbing can cause irritation or dryness, [but it] won't cause permanent wrinkles," Brancaccio said.
The reason is that people do not rub their face constantly, and even when they do, the rubbing doesn't occur in the same place and in the same direction, which would be necessary to cause wrinkles.
"If you're rubbing your face to the point of scarring, that can be a problem, but most people don't do that," Draelos said.
Fact or Myth? Apply moisturizer and foundation in upward strokes or you will get wrinkles.
"You can't rub wrinkles into your face," Draelos said. "The skin is elastic, and when you stretch it, it bounces back."
Even daily repetition won't be enough to cause a wrinkle if it isn't done in exactly the same way each time.
The only way to artificially create a wrinkle is stretching the skin for a prolonged period -- like when you sleep.
"Sleeping on one side of your face all the time can cause wrinkles on that side because you are creasing the skin in the same way night after night," Kauvar said.
"To avoid that, the best thing to do is sleep on your back. But that's not something everyone can control."
Fact or Myth? Drink eight glasses of water a day and you will have great skin.
Answer: Sort of
Drinking water may be important for healthy skin, but eight glasses may be going overboard.
"You do need to hydrate your skin. However, if you drink too much water, it will just be flushed out," Draelos said.
But she cautioned that dry skin can have other causes.
"Drinking water doesn't necessarily hydrate your skin," she said. "If you have dry skin, it's not necessarily because you don't drink enough water."
She said that moisturizer and mild soap may be the best way to help.
Still, dehydration can have harmful effects on skin.
Kauvar explained that collagen -- the substance that gives skin its firmness -- floats in a sugar gel that holds onto water in the skin. So, without water, the skin can lose that rigidity.
"The key thing is that you want to remain well-hydrated," Kauvar said. "There's no absolute number, and it obviously depends on your size.
Fact or Myth? Bathing in milk (or drinking it) can help you have great skin.
Answer: Fact, but before you head to the grocery store...
Milk has a soothing effect on people who have an inflammation of the skin, like eczema, but so do a number of other products whose prices aren't rising at the speed of gasoline.
"Moisturizers and bath additives can do just as well and are probably more elegant," Kauvar said. "There's no advantage to bathe in milk."
Kauvar said that an oatmeal bath could have a similar soothing effect, and given a choice between the two, she would side with the Quaker over the cow.
Brancaccio pointed out that milk does have other soothing benefits, and can be used as a compress for sunburn and rash because it is both moisturizing and lubricating.
"Compresses with milk are very soothing around the eyes," he said. "I use those quite a bit for people with irritation around the eyes. It's very helpful."
And as far as drinking the white stuff?
Milk can be part of a diet that contributes to good skin, but any diet that includes vitamin D and calcium can have the same effect.
There is some preliminary evidence that skim milk can contribute to acne in teenage boys -- a finding attributed to hormones given in cows' feed -- but that study lacks the follow-up to be of concern yet.
"The takeaway message is you want a healthy, balanced diet," Kauvar said.
Fact or Myth? Dry-brushing your skin eliminates cellulite.
"We have very little that will help cellulite, at the moment," Kauvar said.
Superficial fat that grows in globules in the skin is behind this unpleasant phenomenon.
Among current treatments, Kauvar pointed to those that try to increase the thickness of the skin and hide cellulite, and others that try to melt superficial fat in the skin to improve the appearance of cellulite.
Other procedures involve massaging the skin deeply several times a week, which may help cellulite look better temporarily, but need to be done repeatedly.
"There are lots of procedures in development right now, some of which will eliminate or improve the appearance of cellulite, but dry brushing is not one of them," Kauvar said.
So, why do so many snake-oil cellulite treatments garner attention?
Brancaccio says that the skin irritation many of them cause may make it seem like they're working, if only temporarily.
"Some may cause swelling, which gives the appearance that the cellulite has evened out a bit," he said.
In other words, by irritating the skin, the swelling makes the cellulite itself less noticeable. Of course, once that irritation goes away, the cellulite will still be there.
Fact or Myth? Dirt (or chocolate, or greasy food) causes acne.
"Specific food associations with acne have never been demonstrated to have any scientific basis," Kauvar said.
As mentioned before, there was a connection made between skim milk and acne, but scientists couldn't explain why that same connection didn't exist between fattier milks and breakouts.
Kauvar explained that low-fat, low-carb diets seem to show some benefits, but there has been nothing conclusive.
As long as you are a reasonably neat eater, you have nothing to fear from the foods you are eating.
"Vegetable oils, if they get on your face while eating, they can cause acne, but consuming them does not," Draelos said.
Dirt is also not a culprit here.
"Dirt is not the cause of acne, and neither is bacteria," Kauvar said.
Thinking that may lead to its own problems, as over-washing your face and drying it out can cause acne. Face washings should be limited to twice a day, she said. And you should exfoliate to unclog pores, which is different from simply washing your face.
The villain behind acne is sebum, a fatty secretion produced in the skin. When it clogs the pore, a pimple is formed. Efforts to clear up acne should focus on clearing sebum away.
Fact or Myth: Tanning beds can help you avoid sunburn by getting a "base tan."
Answer: Fact -- but don't run out to the tanning salon just yet...
The nice healthy glow of a tan might seem much better than the lobster-like look of a sunburn, but both are bad signs.
"All sun exposure, unfortunately, is harmful to the skin," Brancaccio said.
A tan will let you stay out longer in the sun without getting burnt -- and that's true whether you got your tan at the beach or in the tanning booth -- but those extra rays aren't necessarily a good thing.
"There's nothing healthy about getting a base tan before going out in the sun," Kauvar said. "You may not sunburn as quickly, but that doesn't mean you're avoiding skin damage, which will raise your risk of skin cancer and aging."
Tanning salons have raised controversy in recent weeks with claims that they can boost your health by helping you get vitamin D, but Kauvar said that diet or vitamin supplements can give you vitamin D without the risks.