Does Hair Really Grow Faster In The Summer? We Asked A Trichologist

One myth you've probably heard is that hair — both head and body hair — grows faster in the summer. But is it actually a myth, or do we really trim our hair more frequently as the temperatures rise? To set the record straight, Glam spoke exclusively to International Association of Trichologists-certified trichologist Taylor Rose.

As it turns out, our locks go through four phases of hair growth, which are "primarily influenced by a mix of genetics, hormones, age, and overall health as opposed to seasonal changes, but there are a few factors that may contribute to a slightly faster rate of hair growth in the summer month," Rose told us. "These include increased vitamin D levels due to more sunlight, as well as just being more active/healthy in general."

Vitamin D's connection to hair growth has long been documented. For instance, according to a 2007 research study published in the Journal of Steroid Biochemistry and Molecular Biology, vitamin D directly helps hair follicles function properly, stimulating hair growth. Plus, during the summer, our bodies don't have to put in extra effort to shield us from the cold, thus allowing blood circulation to flow where our hair needs it most: our scalp and skin. Increased blood flow equals increased nutrients and oxygen, leading to better keratin production. And we all know what keratin means for our locks, right?

As Taylor Rose exclusively explained to Glam, vitamin D works wonders for our hair, but summer comes with some downsides, too. "On the flip side, increased sweat from the heat may clog hair follicles if you are not shampooing regularly (more often than in winter months)," Rose told us.

Additionally, if not properly cared for, our hair is more prone to damage and breakage due to exposure to UV rays, thus hindering growth. UV rays oxidize our hair's natural lipids and proteins, turning them dry and frail. What's more, the melanin in our hair acts as a protective layer from harmful UV rays. As such, the lighter your hair color (meaning the less melanin it contains), the more damage-prone it is.

Here's some bad news: As the temperatures rise and we hit the pool for some sweet respite from the heat, we can experience damage from the chemicals in the pool's chlorine. These chemicals deplete our hair's natural oils and the lipids lining our strands. Since lipids lock moisture in our hair, their absence results in dry strands and split ends. Ultimately, this means that summer can help hair grow faster, but it can also hinder our hair if we're not intentional with our haircare routines. So, how can you protect your hair and ensure you get the most of summer's benefits (aka vitamin D supply)?

As Taylor Rose exclusively told Glam, summer conditions favor faster hair growth, but sweat may "clog hair follicles." To avoid this, she advises "shampooing hair more often (every time you sweat)." She also says you can let your "hair air-dry in the summer months and take a few months off of using heat, which usually reduces damage and leads to length retention!" 

Of course, how often you should wash your hair in the summer depends on several factors, but as a general consensus, you need to wash it more frequently than during the colder seasons. Applying a moisturizing mask also hydrates and nourishes the hair, protecting it from harmful sun rays and ensuring that baby hairs don't frizz up when you step out the door. 

But what about winter? How do we protect our luscious lock when the temperatures drop, and the sun's rays aren't as abundant? Rose suggests that you "supplement with vitamin D pills during the winter months (1000 IU) to maintain healthy vitamin D levels (vitamin D is crucial for maintaining healthy hair follicles). Also, shampoo less frequently (unless you are working out / sweating often) to help hair retain moisture, and add in a hydrating hair mask 2x a week." Hydration is key, especially since the winter months lead to "increased hair breakage/damage due to the drier air," but you don't have to rush out and buy expensive hair masks. You can use avocado oil for soft, smooth hair at home — an affordable option for folks with it already in their pantries.