It’s widely regarded as a myth that people’s hair can turn gray overnight. Many urban legends tell of shocking or terrifying events that lead young people– even children– to instantly lose all pigment from their hair. Although it is not true that pigmented hair can turn gray overnight or instantly, there is a surprising amount of truth to this legend.
Aging sneaks up on everyone. Many a baffled 40-year-old has stopped in front of a bathroom mirror, shocked by their hair apparently changing white or gray overnight. In some cases, this occurs directly after an extremely stressful event. In other cases, it occurs without any traumatic preface. Here’s what causes this surprising change in hair color.
How Hair Turns Gray
Human hair doesn’t actually “turn” gray. It grows in like that. As we age, our hair follicles begin producing randomly distributed hairs that lack pigment. As a result, these hairs appear white or gray. At any given time in your life, 9 out of 10 hairs on your head are growing. More and more of these will start coming in gray as you get older.
A single strand of hair, whether gray or pigmented, typically grows for about 3 years before falling out. Each day, you shed about 75 of your oldest hairs, leaving the newer ones behind. When you lose these older hairs, your new, gray hairs become more noticeable.
How it Can Happen “Overnight”
Dark hair is much more noticeable than white or gray hair, so a person doesn’t look gray-haired until most of the pigmented hairs have fallen out. When your gray hair first starts appearing, it is far less noticable than the hair that dominated your more youthful scalp. For this reason, the sudden loss of older hairs can cause you to appear to go gray overnight.
What would cause this? A medical condition known as telogen effluvium dramatically increases your rate of hair loss to several hundred a day— at least 4 times your normal rate of shedding. Sudden, significant weight loss, severe emotional stress, illness, surgery and medications can all contribute to this condition. When you lose several hundred of your older, darker hairs in one day, you are left only with your new hairs– the gray ones. This makes it look like you went gray overnight.
A Grain of Truth
Although telogen effluvium grants some truth to the notion that a person’s hair can go gray overnight because of major stress or illness, it is a myth that you can go from having completely pigmented to completely unpigmented hair in one night. The gray hairs left behind by telogen effluvium were already there, but they were masked by other hairs.
Therefore, you can ignore that urban legend about the kid who went gray because he saw a ghost, and your cousin who swears up and down that his hair went from solid black to completely gray in on night. Even in the event of a serious stress or illness, there is no way that pigmented strands can instantly change colors.
Source Used- Intellihealth- The Science of Gray Hair