The Truth About the 7-Year Hair Cycle

Take a moment and scroll back through your old photos. You might notice that your hair used to be thicker, shinier, or a completely different color altogether. If you've ever heard that your hair "completely changes every seven years," you're not imagining things there's some science behind that belief.

It turns out your hair is constantly evolving thanks to its natural growth cycle. And while you’re not shedding your entire mane all at once, over the course of several years, almost every strand on your head is eventually replaced. Here's what’s really happening under the surface and why your hair changes as you age.

How Hair Grows

Human hair grows in a continuous loop of three distinct phases:

• Anagen (growth phase): Lasts 2 to 6 years and accounts for about 85–90% of the hair on your head at any time.

• Catagen (transitional phase): Lasts 2–3 weeks and involves the hair detaching from the blood supply.

• Telogen (resting phase): Lasts about a year, during which the hair falls out and the follicle rests before growing a new strand.

You naturally lose between 50 to 100 hairs a day, especially while brushing, shampooing, or styling. After each strand falls out, its follicle stays dormant for several months before producing a new one.

“Each hair is a living entity with an average duration of two to six years,” says Jeffrey Hsu, MD, a board-certified dermatologist and co-director of Oak Dermatology in Chicago. Since each hair operates on its own individual timeline, the process isn’t synchronized which is why your hair doesn’t all fall out at once.

So, Do You Really Get a Whole New Head of Hair Every 7 Years?

Yes and no. While it's true that most of the hairs on your head today weren’t there seven years ago, not all of them fall out and regrow at the same time. Some strands might only be a few months old, while others have been around for years. According to Dr. Hsu, roughly 1 to 3 percent of follicles are dormant at any given time.

“Different hair follicles are in different phases of the hair cycle because there is no synchronization, which allows you to have constant density of hair,” adds Rohit Kakar, MD, a board-certified dermatologist and director of Orchard Lake Dermatology & Cosmetics.

It’s also worth noting that seven years is generally the upper lifespan of a strand, but that doesn't mean all of your hair sticks around that long. Your personal growth cycle may shorten with age, and it’s also influenced by factors like:

• Hormonal changes (e.g., pregnancy, menopause)

• Stress

• Illness or infection

• Damage to the follicle (from heat styling or tight hairstyles)

How Hair Changes as You Age

If your hair doesn’t feel the same over time, that’s because it’s not. As you age, the strands that regrow tend to be different in texture, color, and even volume than the ones that fell out. Here are some of the most common changes:

• Thinning strands: As hair’s growth phase shortens, the diameter of each strand becomes smaller. Over time, this makes your hair appear less full or voluminous.

• Dryness and coarseness: Sebum, the natural oil produced by your scalp, declines with age. Less oil means less softness, shine, and smoothness.

• Graying: Hair turns gray when pigment-producing cells (melanocytes) within the follicle die off. Once they’re gone, the hair grows back without color.

And while these changes are completely natural, they don’t mean your hair health has to decline. Eating a diet rich in protein, vitamins A and C, and iron can support healthy follicles. Gentle styling, scalp care, and minimizing heat damage can also help maintain hair quality as you age.

The Bottom Line

The idea that your hair changes every seven years isn’t exactly a myth it’s more like a simplification. While all your strands don’t fall out on a set timeline, most of your hair is continuously replaced over several years, meaning the locks you have today are mostly new. And thanks to age, hormones, and life stressors, they may not look or feel the same as they once did and that’s perfectly normal.

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