Why Does Blonde Hair Turn Brown? Understanding Why Natural Blondes Sometimes Experience Color Change

Many people with naturally blonde hair often find themselves wondering why their once golden locks gradually darken to various shades of brown as they age.

This common phenomenon, which can be a source of curiosity or even frustration, is rooted in a mix of genetics, environmental factors, and biological changes. 

dr joe cincotta

In this article, we'll uncover the science behind why blonde hair turns brown and offer insights into what can be done to maintain those cherished blonde tones for as long as possible. 

We sat down with Dr. Joe Cincotta, our inhouse chemist, to get his take on why this happens, too!

First – Let’s Understand The Role of Melanin in Hair Color

Before diving into the specifics of blonde hair turning brown, it is important to understand the role of melanin in hair color. 

eumelanin (dark brown to black pigments) and pheomelanin (yellow, red and light brown pigments)

Dr. Joe explains:

"Melanin are pigment granules that gives color to our hair, skin, and eyes. There are two main types in hair: eumelanin (dark brown to black pigments), which makes hair dark, and pheomelanin (yellow, red and light brown pigments), which gives lighter hair colors such as blonde and red. 

melanocte (hair bulb)

Specific cells at the base of the follicle (the hair bulb), called melanocytes, produce melanin pigments which are released directly into hair keratinocytes which eventually harden and become the hair shaft.

The size and type of melanin pigments one possesses determine the color of your hair. Melanin goes through significant pigmentation changes throughout a person’s life.

In other words, your hair color doesn’t stay the same color. This is why a blond child may become closer to a brunette in their teen and adult years. 

The sun's UV rays can break down (oxidize) your hair's melanin. People with dark hair who have more eumelanin may notice a slight lightening (red highlights) after a few hours in sunlight, while others may never notice a difference. 

But those with blonde or red hair have mostly pheomelanin, which is more easily oxidized by sunlight, will see significant lightening of their hair color."  

Here Are 8 Reasons Why Your Blonde May Be Turning Brown

Blonde hair turning brown is a phenomenon that can be attributed to several factors. Some of the reasons blonde hair turns brown are internal and systemic, other reasons are external exposures. 

  1. Genetics: The primary reason for why your hair color changes over time  lies in genetics. Blonde hair has less melanin, particularly eumelanin, compared to brown or black hair. As individuals age, their predetermined genetic programming can “order” an increase in melanin production which gradually darkens hair color.

  2. Age: With aging, the activity of melanocytes, the cells that produce melanin, changes. In childhood, these cells might produce less melanin, resulting in blonde hair. However, as one grows older, the melanocytes can become more active, leading to the production of more melanin and, consequently, darker hair.

  3. Hormonal Changes: Hormonal fluctuations, especially during puberty, pregnancy, and menopause, can affect melanin production. These changes can result in blonde hair darkening over time. For instance, increased levels of certain hormones can stimulate melanin production, leading to a gradual shift from blonde to brown.

  4. Environmental Factors: Exposure to the sun can also play a role in changing hair color. The sun's ultraviolet rays can break down melanin in the hair over time, leading to a lighter hair color initially. However, prolonged exposure can stimulate the production of more melanin as a protective response, eventually resulting in blonde hair going darker.

  5. Hard Water: Hard water contains high levels of minerals like calcium and magnesium, which can build up on the hair, leading to changes in texture and color. This mineral build-up can make blonde hair appear darker or more brassy over time as it coats the hair strands, interfering with the natural hair color (or chemicals, if the hair has been color-treated). 

  6. Nutritional Factors: Nutrition and overall health can influence melanin production and hair color. Deficiencies in certain vitamins and minerals can impact melanin production, potentially affecting hair color over time.

  7. Chemical Exposure: Regular use of certain chemicals, found in swimming pools or hair products, can also affect hair color. For example, chlorine exposure can cause blonde hair to take on a greenish tint, while overuse of some hair products can lead to hair damage and color change.

    You can read more about how to protect your hair from chlorine in our guide.

  8. Product Buildup: Product buildup is another culprit, as the residue from shampoos, conditioners, and styling products can accumulate on the hair, weighing it down and contributing to blonde hair darkening. This is especially noticeable in lighter hair shades, where even a slight change in color can be quite apparent.

How Do I Keep My Natural Blonde Hair From Darkening?

Now, if you’re like us, and super vested in your blonde hair, you make it your mission to keep your color fresh and bright.

At Color Wow, our commitment to helping you keep your optimal color is just as fierce. Which is why we’ve gone above and beyond industry standards to protect it. 

Today's clean beauty standards have restricted 30 ingredients in the United States and 1,400 in the European Union from being used in personal care products.

At Color Wow, we've banned them all, PLUS we've identified an additional 70 ingredients commonly found in other hair care formulas that can dull, darken and distort your color.

From our award-winning color-safe products to easy everyday habits, here are our top tips for how to keep natural blonde hair from darkening:

1. Protect Against Sun Exposure

Wear hats or use hair products with UV protection to shield your hair from the sun, which can stimulate melanin production and darken your hair. Learn more tips for protecting your hair in the sun here.

Here are a few of our fave products with UV protection:

color wow pop and lock
Pop + Lock High Gloss Finish

Smooths frizz, temporarily seals split ends, prevents color fade, imparts an epic shimmery shine. Heat protectant.

color wow cult favorite
Cult Favorite Firm + Flexible Hairspray

Lightweight spray for all-day, flexible, brushable, touchable hold. Non-yellowing. Heat protectant.

color wow one minute transformation
One-Minute Transformation

On-the-spot frizz fix smooths, tames and depuffs hair for silkier, shinier results in just one minute. Heat protectant.

color wow money mist

Money Mist

Luxe, light leave-in conditioner for instantly stronger, glossy, expensive-looking hair. Heat protectant.


2. Moisturize Regularly

Keep your hair well-moisturized to maintain suppleness, resiliency and keep it protected. Use hydrating hair masks or oils suited for blonde hair. 

chris appleton and color wow's money masque
Money Masque is our deep hydrating hair treatment suitable for ALL hair types.

Its weightless formula leaves no waxy, heavy buildup – and it’s also celeb stylist Chris Appleton’s 1-step-prep for luxe, super healthy hair!


3. Use Gentle, Non-Stripping Hair Products

Opt for sulfate-free shampoos and conditioners specifically designed for blonde hair to avoid harsh chemicals that can strip natural oils and contribute to darkening.

Our top picks? 

color wow color security shampoo

Color Security ShampooThe only 100% clean, sulfate-free formula that leaves no residues behind to dull your color. Made with a unique blend of 8 non-stripping cleansers (including a super gentle Japanese amino acid often found in face washes), this formula was independently tested and shown to keep the cuticle smooth and closed, to help keep color from leaching out.

color wow color security conditioners
Color Security Conditioners (either fine-to-normal or normal-to-thick):

These are packed with carefully-vetted, nourishing ingredients that won’t oxidize and yellow your color.


curl wow hooked shampoo
Hooked 100% Clean Shampoo: for curly girls, our Hooked shampoo is 100% clean and non-stripping, just like our Color Security Shampoo, but with an added bonus. It’s formulated with root-locking tech that helps anchor hairs in the follicle for reduced shedding.


4. Limit Heat Styling and Chemical Treatments

Reduce the use of heat styling tools and avoid chemical treatments as much as possible, as these can damage your hair and affect its color over time.

At Color Wow, we include 2-3 types of heat protection in all of our leave-in treatments and styling products, so you’re always protected against heat damage.

5. Fight the Effects of Hard Water

Most people don’t think twice about the water they use to shampoo their hair. But at Color Wow, we realized your blonde can never be its lightest and brightest if there are minerals interacting with the color. And these minerals are in everybody’s water.

color wow dream filter

That’s why we developed Dream Filter Pre-Shampoo Mineral Remover.

In just 3 minutes, it works like a magnet to lift off water-born color corrupters that dull, darken and distort your color.
The result? Lighter, brighter, shinier color!

before and after using color wow dream filter

Instyle editor Victoria Moorhouse put Dream Filter to the test and here’s what she had to say: 

“I’m aware that hard water can darken or warp your hair color. I also know the minerals and metals in this water can build up on your hair, making it feel stiff and rough and look pretty dull. 
this treatment... brightened up my lighter blonde highlights. it looked like i had just left the salon with a gloss!

But, up until a few days ago, these facts have never really meant anything to me because I don’t think I had ever experienced the opposite! (After using Dream Filter) I was astonished by how weightless my hair felt.

It was clean without being squeaky, stripped, or dry. It felt like a coating that had been on my hair for 27+ years had been removed. My hair was silky! This treatment … brightened up my lighter blonde highlights. It looked like I had just left the salon with a gloss!”

Coming to grips with the reasons behind
blonde hair turning brown is crucial for maintaining the desired color and vibrancy.

Factors such as environmental exposure, hair care practices, and the natural aging process all contribute to these color changes. By implementing appropriate preventative measures and seeking professional treatments when necessary, you can ensure your blonde hair remains beautiful and free from unwanted color shifts!


Read more about hair science on the Color Wow Blog:

Dr. Cincotta holds a Ph.D. in Organic Chemistry from the City University of New York, and is currently VP of Research + Development at Color Wow.

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