Trimming your hair regularly makes it grow faster.
New hair has a tapered or a pointed tip. When the tip is trimmed, the end becomes blunt, making the hair appear thicker, says Paradi Mirmirani, M.D., assistant professor of dermatology at the University of California, San Francisco. Bottom line: Trimming doesn’t help your hair grow, but regular cuts make your mane look healthier by eliminating split ends, tangles, and breakage. You can stimulate hair growth by eating a well-balanced diet that includes plenty of protein, which is mostly what hair is made of, Mirmirani says.
If you pluck a gray hair, two will grow in its place.
Myth! If you pull out a hair, only one will grow back. "It is not possible to have more than one hair fiber growing out of one hair shaft," says Mirmirani.
Fish oil stimulates hair growth.
Not getting enough of the kind of fatty acids found in fish oil may lead to hair loss, according to one study, but the fatty acid directly linked with hair growth is actually Omega-6, commonly found in meat and vegetable oil. Most Americans get enough of that in their diets, so supplements aren’t necessary, according to the University of Maryland Medical Center.
Stress can make you go gray overnight.
Your hair color grows from the root and doesn’t change once it’s grown out—no matter how bad your day has been. But too much stress may cause hair loss or premature graying, if you’re genetically predisposed to it. (Need to de-stress? Try this two-minute breathing exercise.) “Genetics is the main determinant of how much you gray," says Mirmirani "But environmental factors, such as smoking, may lead to more gray."
If you brush your hair 100 times before bed each night, it will grow longer and thicker.
Brushing may actually damage your hair. "Hair is like any other fiber—for example, wool—and is prone to wear and tear, which can lead to breakage, loss of luster, and decreased manageability," Mirmirani says. "The friction from that much brushing can lead to more wear and tear." To cut back on the damage, she recommends smooth plastic combs and brushes instead of bristle brushes. And too much washing and coloring can make the problem worse.
Your hair continues to grow after you die.
Even some doctors believe this myth, according to a study published in the British Medical Journal. While dehydration of the body after death may make it seem like hair and nails are growing, they are not.
Bonus Myth: Shaving or waxing will make your body hair grow back thicker.
Shaving does not change either how fast body hair grows or how much returns, according to research published in the Journal of Investigative Dermatology. But shaving causes the tip of your hair to become stubbly and blunt while it regrows, which may make it feel like it's thicker or even appear darker, according to the Mayo Clinic.