While aging is a beautiful privilege, time does have a biological impact on your hair and scalp. However, when you have all the information about what’s going on and why, it can help some of those oh-no-I-am-going-gray feelings start to dissolve and make room for a gentler approach to embracing change. In fact, celebrating these natural processes can make you feel even more confident every year (with help from biology-first haircare solutions to mitigate any concerns that may arise). 

We tapped Dr. Rachael Williams, K18 Senior Hair and Scalp Scientist, to break down all the behind-the-scenes hair biology—plus, her biotech-backed protocol to keep hair thriving at every age. 

so, why does hair age?

Let’s start with the basics. Just like our skin, hair ages due to a combination of completely normal biological factors—including genetics, hormonal shifts, slower follicle renewal, less oil production, and reduced scalp circulation. That’s not all though. 

“Genetics influence how we age, but environmental and lifestyle factors can be why some people experience premature aging while others do not,” explains Williams. “Nutritional deficiencies, UV exposure, psychological stress, and oxidative stress can significantly affect hair density, color, and overall quality.”

This means that everyone’s hair journey will look a little different as they get older, as it ultimately depends on a variety of controllable and uncontrollable factors. 

the most common signs of aging hair

Here’s a few changes you might see over time, and an explanation of what’s happening beneath the surface. 

graying

It may start with just a few silvery wisps around your hairline, but graying is one of the prevalent signs of aging hair. 

“Gray hair happens due to a loss of pigment called melanin within the hair follicle and fiber—this is what gives the fiber its color,” says Williams. “This pigment is created by cells within the hair follicle called melanocytes, and as we age, the amount of melanin produced can decrease, as well as the number of melanocyte cells that make it.” 

While grays are incredibly common and normal, their texture—coarser, wirier, or more resistant to styling—might surprise you. That’s because gray fibers have their own unique structure, which can affect how they behave and reflect light.

thinning

No one likes to think about their hair thinning, but unfortunately it’s an aspect of aging that impacts many of us. 

“Hair density peaks in the late 20s, and the actual size (diameter) begins to decline in the mid-30s,” says Williams. She adds that density refers to the actual number of hair follicles, which are usually grouped into small units of follicles. As we age, this can decrease to one or two follicles within the unit, reading to reduced density. 

“The hair may still be there, but it has miniaturized, meaning the hair follicle shrinks and is more like the downy hairs you find on the face as opposed to the thick terminal scalp hairs,” explains Williams. “The changes in diameter also arise from this miniaturization—as the hairs get finer, they also become thinner, resulting in the overall hair body feeling thinner.”

Additionally, thinning is impacted by hair breakage, which we become more susceptible to with age because our strands are weaker and finer. 

dullness 

Sebum + oil production is often thought of as the enemy but it actually plays a huge role in how soft and shiny your hair looks on a given day. Unfortunately, the amount of sebum we make—you guessed it—declines with age. 

“Hair follicles are connected to sebaceous glands that produce oil that gets wicked up onto the hair fiber, affecting shine and fullness, as well as texture,” says Williams. “As we age, the amount of oil and the composition alter, especially during peri- and post-menopause, which can leave the scalp feeling dry and the hair looking dull, feeling coarse, and prone to frizz.”

coarser texture

As noted above, sebum production and texture changes also go hand-in-hand—however, oil isn’t the only factor at play. 

“Coarseness can also be due to structural changes within the fiber and damage to the hair cuticle,” explains Williams. “And with aging, the fiber and the surrounding cuticle are more prone to damage from heat, styling, and chemical services, which can result in coarser, frizzier, and duller-looking hair over time.” 

curl pattern changes

Curl patterns can also be impacted as we age—for instance, strands that were once straight may become wavy, or curls may get looser and less uniform. 

“There is limited research on changes in curl pattern with age, and we would assume changes are due to hair fiber structure changes and alterations in the keratin disulfide bonds,” explains Williams. “Thinning fibers, a more damaged cuticle, and the presence of greys, which have their own texture, could all contribute to changes in the curl pattern.”

While aging—and the impact it has on your hair and scalp—is inevitable (and beautiful!), there are ways to help slow down the adverse effects it has on your hair.