If you are in shock or frightened, your hair can turn white.

FACT! The phenomenon of hair turning white from fright (or shock or grief or stress) persists in literature, poetry and even a handful of medical journals. But is there any truth to the rumor that we can actually scare our hair?

Yes and no, says dermatologist Dr. David Orentreich, associate director of the Orentreich Medical Group in New York and assistant clinical professor in the department of dermatology at Mount Sinai School of Medicine.

“It’s appealing on a literary or poetic level that a person’s experience could be so severe or terrifying that they age overnight,” he says. “But you can’t lose pigment in your hair. Once it leaves your scalp, it’s non-living; it’s dead.”

But, Orentreich says, while fear can’t suddenly cause your hair to turn white, there is a medical condition that could make people think it has.

The hair of Nancy Thompson, played by Heather Langenkamp, suddenly starts to turn white after Freddie Kruger torments her in her dreams in 1984’s “Nightmare on Elm Street.”

Alopecia areata is an autoimmune condition that attacks hair follicles, causing pigmented hair such as black, brown, red, or blonde to fall out, leaving the gray and white nonpigmented hairs behind. (Eventually most people lose all their hair entirely.)

“If someone has salt-and-pepper hair – a mixture of gray and black – and they develop alopecia areata, the dark hairs can fall out quickly,” he says. “So it appears that they’ve gone gray overnight.”

Stress, as it turns out, may be a trigger for some autoimmune disorders.

“It’s conceivable for a person who has a tendency for alopecia areata to go through a stressful experience which makes it flair up and the first thing that happens is their dark hair falls out,” he says. “And that can happen quickly – in days or weeks – leaving just the gray hair.”

Although autoimmune diseases have been around forever, Orentreich says it’s only been in recent years that doctors have come to understand their impact.

“These phenomena would occur but they were completely mysterious,” he says. “No one had any inkling that the immune system could cause hair to fall out. There was only a primitive understanding – if any understanding – of the immune system.”

Fear, shock or grief, on the other hand, were something people could wrap their brains around, which probably explains why emotions play a huge part in most of the stories about hair turning white overnight.

According to a 2008 paper in the Journal of the Royal Society of Medicine, the first documented case of sudden hair whitening was in the Talmud in 83 A.D. The victim was a 17-year-old boy who was appointed chief of the main Israeli Talmudic academy. His sudden white hair was said to have been a “consequence of strenuous studying.”

In later years, the phenomenon was attributed to Marie Antoinette, whose auburn locks supposedly turned ghostly white the night before she lost her head to the guillotine and to Shah Jahan of India after his favorite wife died (he went on to build the Taj Mahal in her honor). Even sharpshooter Annie Oakley reportedly fell victim at age 41 after she was involved in a horrific train accident (an alternate story claims her white hair was the result of an overly hot bath).

In the ’80s “Nightmare on Elm Street” horror movie franchise, a shock of the heroine’s hair turns white after she is terrorized in her dreams.

There have been reports of sudden blanching as a result of bear attacks, ill-advised bets, shipwrecks, adultery and the death – or serious injury – of a loved one. A 1902 British Medical Journal even described the case of a 22-year-old woman who witnessed a woman’s throat being cut and got up the next morning to find half her pubic hair had turned white.

According to Orentreich, though, even white pubic hairs could be explained by the autoimmune disease.

“When it attacks hair, sometimes the hair will keep growing with no pigment,” he says.

Alopecia areata may not be the only explanation for this hair-razing condition, though. Researchers who have studied historical references to the phenomenon also believe a “sudden” change in hair color could also be traced to hair dye simply washing out.

“If you get your hair colored today and then stop getting it colored, it takes a number of weeks or months for the gray to grow out,” says Orentreich. “But years ago, the dyes weren’t permanent. It could be something like that.”