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What Is Hair Serum? | Pros, Cons, and Our Top Picks

What Is Hair Serum? | Pros, Cons, and Our Top Picks

If you don’t have a good hair serum in your weekly routine, you’re missing out. Learn about this versatile hair product, which hair types it’s best for, and how to use it for shiny, soft, frizz-free hair.

Considering Hair Serum?

Fit young gal in a white tshirt with curly hair applies hair serum to her fingers before running her hands through her hair

Progressman/Shutterstock

If you take a peek into your bathroom closet, you’ll see a variety of hair products in different forms. Most of us have mousses, gels, creams, treatments, and oils galore. But what about hair serum?

Many people don’t realize just how essential a good quality hair serum is. These lightweight formulas are designed to banish the most formidable hair foes, from frizz and dullness to heat damage and rough texture. 

A good hair serum just might be the new lynchpin of your hair care routine. But if you’re not familiar with this type of hair product, what it does, and how to use it, you’re in luck. We’re going back to basics with this guide to cover everything you need to know about hair serum. 

We’ll talk about:

  • What hair serum is
  • Benefits and drawbacks
  • How hair serum works on each hair type
  • Best hair serum for your hair type
  • What you should know before using

It’s important to do a little research before choosing a hair serum to ensure you’re picking one that’s right for your hair type and needs. We’ve got you covered! Get the skinny on hair serum and how to work it into your hair care routine below. Let’s get started!

First, What Is Hair Serum?

For a piece on what is hair serum, a brunette woman pouring some of the oil into her hand while standing in a white shirt with a blurry background

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Hair serum is a thin, topical hair product that contains concentrated active ingredients meant to nourish hair, eliminate frizz, increase shine and softness, and provide damage protection.

Unlike creams and oils, lightweight serums deliver the active ingredients to your hair in a concentrated dose without weighing it down too much. 

Hair serum is usually silicone-based with nourishing ceramides (fats) and amino acids (proteins) that actually help build, repair, and fill in the surface of your hair for a smoother texture.

It’s like a nutrient-rich shot that coats your hair with just the right amount of slip, smoothness, and softness.

But if you’ve sworn off silicones, no worries! There are tons of effective serums available that are formulated to be silicone-free (you’ll see our favorite silicone-free serum later in our guide).

What Hair Serum Does

By coating the hair with a very thin layer of potent active ingredients, hair serum is able to smooth the roughest hair texture, eliminate frizz from the coarsest or curliest hair, and protect the hair from potential heat or environmental damage. 

It’s also designed to make hair feel very soft to the touch. Our favorite serums leave a delicious scent lingering in your locks and impart a beautiful, natural shine. 

Hair serums can be used on dry, damp, or wet hair. Depending on your hair type and texture, you might benefit from using a hair serum before or after you style your hair, on off days between shampoos, and whenever your hair needs a quick pick me up. 

Now that you’re a little more familiar with what hair serum is, let’s take a look at the benefits and drawbacks. 

Hair Serum Pros and Cons

Hair serum is hailed by some beauty gurus as a miracle, all-in-one product. We tend to agree – at least when we’re talking about our favorite serums – but that’s not the whole story. There are both pros and cons to using a hair serum. We’ll lay out the benefits and potential drawbacks here. 

Hair Serum Benefits

A good hair serum offers plenty of benefits. If you dream of frizz-free, soft, shiny hair that looks and feels its best, it can deliver. Here are the benefits of using a hair serum that’s right for your hair type. 

Eliminates Frizz

For a piece on the best hair serum, a woman with frizzy hair pouts as she looks at the camera

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Frizz comes with the territory if your hair is coarse or curly, and it’s not uncommon to struggle with frizz and flyaways if your hair is straight. Hair serum targets frizz and flyaways by leaving a very thin film on top of the hair that prevents these issues from flaring up. 

Many formulas contain proteins that remove any static charges in your hair that lead to frizziness. Hair serum is lightweight, but it’s heavier than your strands and provides just enough counter weight to stop frizz and flyaways from turning your ‘do into a don’t. 

Smooths Hair Texture

Without frizz and flyaways, hair looks smoother by default. But that’s not the only way a good hair serum smooths out your hair texture and feel. Ceramides, which most hair serums contain, are fats that encourage the outer layer of your strands (the cuticle layer) to lie down flat. 

This creates smoothness in the hair, but that’s not all. The amino acids (protein building blocks) in many hair serums help smooth hair, too. Amino acids fill in the little natural gaps in your outer cuticle layer the same way a road crew fills in a pothole. 

And if you’re using a serum formulated with silicones, the soft coating they leave on the hair adds to the smoothness. The result is a polished, even surface on every strand and overall smooth locks.  

Increases Shine

Woman with long thick hair holds the end and looks to her right in a side profile

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Smooth, flat surfaces better reflect light than uneven, rough surfaces. When you use a hair serum that smooths your hair, you’re going to notice that your hair is shinier than ever.

The ceramides, amino acids, and silicones in serums make your hair mirror-like by filling in gaps in the hair’s surface for the ultimate shine. 

Enhances Straight, Wavy, or Curly Hair Texture

Lots of hair products promise to eliminate frizz, create smoother hair, and increase shine. But not many can provide equal benefits to wildly different hair types. This is where hair serum starts to look more like a miracle product.

Hair serums can bring out and enhance your natural hair texture, whether it’s straight, wavy, curly, or kinky. Because this product coats the hair with a very thin film, it acts like a thin cast to help encourage strands to embody their natural shape (whatever that may be). 

There are serums available for straight, wavy, curly, and coily/kinky hair. Since the formulations are so light, hair serum is one of those rare products that can work for every hair type if used correctly. 

Provides Damage Protection

Lady who did not ask "what is hair serum" looks at the split ends of her damaged hair

Mehmet Dinler/Shutterstock

Any product that coats your hair can help protect against damage, and hair serum is no exception. You can prevent damage from common sources when you use a good hair serum. 

With this product in your hair care routine, you can prevent damage from:

  • Chemical processing (color, bleach, straightening treatments, etc.)
  • Physical wear and tear (brushing, styling, weathering, etc.)
  • Heat styling (flat iron, curling iron, hair dryer, etc.)
  • The elements (sun exposure, chlorine, wind, etc.)

Just make sure you’re applying your serum before any heat is applied to your hair if you plan to use it as a heat protectant. It’s also smart to check the bottle or manufacturer’s website to find out the maximum temperature it will protect against. 

Hair Serum Drawbacks

Hair serum has tons of benefits, but it’s not perfect. Here are the potential drawbacks of using a hair serum.  

Application Learning Curve

Woman applying hair serum to her hair while holding it in her hands

Parilov/Shutterstock

Applying hair serum is the first roadblock you might run into when you decide to try this product. Hair serum has a thin viscosity, but it’s still got a slightly thick consistency.

You might find it difficult to evenly apply it to strands because it doesn’t move around as easily as, say, an oil. To work around this drawback, just massage the serum in your palms for about 5 seconds to gently heat it and thin it out for easier application. 

Product Buildup Concerns

Hair serum works its miracles by coating the hair – that’s how you get smoother, shinier, frizz-free locks when you use it. The downside of that is that coating the hair can result in product buildup.

You’ll need to use a good clarifying shampoo or apple cider vinegar rinse each week to ensure you’re not allowing serum to slowly build up on your strands. Product buildup not only leaves your hair feeling dirty, but it can also suffocate your strands and prevent them from receiving the moisture it needs.

So if you decide to start using hair serum, make sure you’ve got a way to clarify and cleanse your hair thoroughly to avoid product buildup

Can Make Hair Look Greasy

Middle-aged girl holds her hair between fingers that are greasy because she did not read our guide on what is hair serum

Natali_ploskaya/Shutterstock

If you have super-coarse or curly hair that hardly ever looks greasy, this likely won’t be a concern for you. But finer hair textures and straight hair – especially if you struggle with oily hair to begin with – have to be very careful with hair serum to avoid looking greasy. 

This product is lightweight in comparison to some heavier products, but it’s still heavier than water. If you apply hair serum to your roots or apply too much, it can make your hair look greasy, not shiny.

If you’re the type that can’t apply conditioner to your roots, follow the same rule with hair serum. And use it sparingly – a little of this goes a long way. 

Best Hair Serum for Each Hair Type

We’ve got the basics and the pros and cons sorted. Now, let’s zero in on finding the right hair serum for your hair type. First, a quick refresher on hair types. 

How to Identify Your Hair Type

Different types of hair on a scale, from 1 to 4c to help answer what is hair serum

Tales of Stars/Shutterstock

Your hair type consists of two general characteristics: Your hair’s texture and strand shape. The texture of your hair refers to the thickness of each strand. If you have fine hair, each strand is thinner than a thread.

If you have medium hair, each strand is about equal to a thread. And coarse hair is thicker than a thread. The second part is your hair strand shape. It may be straight, wavy, curly, or coily. When you lump your hair’s texture and shape together, you get your official hair type. 

Type 1: Straight

Straight hair isn’t wavy or curly at all. It may have trouble holding a curl when heat styled. Straight hair may get oily faster than other hair types. 

Type 2: Wavy

Wavy hair isn’t quite curly, but it has more bend in it than straight hair. Wavy hair sometimes struggles with getting oily fast, usually when the texture is fine. 

  • 2A: Fine with slight wave
  • 2B: Medium with waves (can be frizzy)
  • 2C: Coarse and very wavy (tends to frizz)

Type 3: Curly

Curly hair has more bend in it than wavy, and the bends form complete curls from root to tip. Curly hair typically doesn’t struggle with oiliness, but frizz and dryness can be a problem for this hair type. 

  • 3A: Fine or medium with curls (can be frizzy)
  • 3B: Medium or coarse with tight curls (tends to frizz)
  • 3C: Coarse with very tight curls (usually frizzy)

Type 4: Coily

Coily hair is very tightly coiled or kinked in small curls. It tends to be dry, frizzy, and coarse in texture.  

  • 4A: Coarse with tightly coiled curls (usually frizzy)
  • 4B: Coarse with very tight coils (usually frizzy)
  • 4C: Coarse with extremely tight coils that may not resemble complete curls (usually frizzy)

Now that you know your hair type, let’s take a look at the best hair serum for your type. 

Best Hair Serum for Straight Hair

Best for Wavy & Straight Hair
Garnier Fructis Sleek and Shine Anti-Frizz Serum
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If you’re Type 1 (1A, 1B, or 1C) with straight hair, you need a lightweight hair serum that won’t make your hair look greasy or weighed down. The best serum for straight hair is Garnier Fructis Sleek and Shine Anti-Frizz Serum.

It can be used on any hair type, and reviewers with fine, curly hair saw great results, but this is the gold standard for straight hair. It does contain silicones and argan oil, which are heavier ingredients that straight-haired folk typically avoid.

But you use such a small amount of this serum that it won’t weigh even pin-straight looks down. If you want straight hair that is sleek and shiny without looking greasy or lifeless, this serum will get you there. 

Nourishing argan oil, plum extracts, and apricot kernel oil envelop your hair in a sweet-smelling matrix that conceals damage and makes hair soft, sleek, and shiny with plenty of body. It has a great 4.6 star review average on Amazon. More than 12,200 reviewers agree that if you have straight hair, this is the serum you need to try. 

Best Hair Serum for Wavy Hair

Best for Wavy Hair

Wavy hair (type 2) is somewhere between straight and curly with properties of each hair type. Whether you’re a 2A, 2B, or 2C, your waves will thank you for using Redken Curvaceous Full Swirl Cream-Serum.

This wave-enhancing serum is known for bringing out the waves you have and providing just enough moisture and nutrients to nourish the hair without overwhelming it. This serum is really a 2-in-1 product because it’s a cream mixed with a serum.

The formula is designed to eliminate frizz, lock in moisture and hydration, and keep humidity from making your hair go *poof.* Reviews show that both wavy and curly girls love this serum, but we like it best for wavy hair because it can turn the loosest bends into sexy, beachy waves that stay frizz-free for 3 days.

If you have wavy hair, you know this is an amazing claim. But it’s true! Thousands of reviewers have given it a 4.6 star average rating. We’d call this a 5-star product for sure. 

Best Hair Serum for Curly Hair

Best for Curly Hair
John Frieda Frizz Ease Extra Strength Hair Serum
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Curly hair (type 3) needs a few specific things from a hair serum. It tends to be dry, so it needs moisture to feel soft, look shiny, and revive curls. Curly hair is also prone to frizz and flyaways, so the serum needs to be heavy enough to tame the beast.

John Frieda Frizz Ease Extra Strength Serum must’ve heard about our curly girl problems, because this serum deliversIt eliminates frizz and flyaways, literally repels curl-ruining humidity, provides heat protection, and physically repairs weathering and damage on the surface of strands.

It contains bamboo extract, which is used to increase scalp blood circulation for healthier, faster-growing hair and soothe the scalp. You can use a pump of this serum in soaking wet hair and allow it to dry to get the best results.

If you have fine curly hair (3A), don’t apply it to your roots. It’s not a super heavy formula, but it can weigh your roots down if applied too liberally. Nearly 10,000 reviewers give it 4.5 out of 5 stars. That’s a great indicator of a quality product. 

Best Hair Serum for Natural Hair

Best for Natural Hair
GK HAIR Global Keratin 100% Organic Argan Oil Serum
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Natural or coily hair (type 4) has all the concerns of the curly type plus a few more. Dryness, frizz, flyaways, and fragility are all part of having natural hair. Until you use Global Keratin 100% Organic Argan Oil Hair Serum.

This potent hair serum targets every issue girls with natural hair tend to struggle with. The formula contains keratin, which is the protein that makes up hair. The keratin infusion literally plumps every strand of hair for smoother, stronger locks.

Argan oil is also in the mix, and it’s been proven to be one of the best, lightweight oils for nourishing and increasing shine in black hair.

Whether your kinky curls are big and bodacious or tightly curled like a corkscrew, reviewers say this formula will enhance your strand’s natural shape for the best hair days you’ve ever had. Glossy, shiny, bouncy, and nourished coils that better stand up to damage and repel humidity? Yes, please. 

Work the serum into clean hair that is either damp or dry (it’s up to you). Reviewers give it an amazing 4.7 out of 5 stars on Amazon. We’d give it a solid 5 stars. It’s worth grabbing if you have natural, coily hair! 

Best Hair Serum for Damaged Hair

Best for Damaged Hair
Herstyler Hair Repair Serum - Argan Oil Hair Serum, Vitamin E Hair Serum and Aloe
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Any hair type can sustain damage from chemicals, heat, the elements, or physical wear and tear. That’s why it’s hard to find a good hair serum that can work on any hair type from straight and fine to coily and coarse. But we finally found the one! It’s Herstyler Hair Repair Serum

This product has gone viral thanks to BuzzFeed and TikTok. It works to repair damage on all hair types. The formula isn’t greasy or heavy, so it can be used on fine hair without turning your locks into a grease pit.

It contains argan oil and aloe, which are highly nourishing and moisturizing anti-frizz ingredients we like to see in serums for medium, coarse, wavy, or curly hair. Damaged hair tends to tangle easily, have a lot of frizz, suffer breakage, and look generally dull.

This serum corrects those problems to make hair soft, shiny, frizz-free, smooth, and strong. It also delivers a dose of follicle-restoring vitamin E to ensure new growth is healthy and nourished. 

If you have fine or straight hair, you may only need to apply one or two drops of this serum to your hair. Medium, coarse, wavy, and curly types can start with two or three drops for the best results. 

Things to Consider

Behind shot of a woman using hair serum while holding her hair in her left hand and looking right

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Before you start using a new hair serum, we have a few helpful tips to share with you. These will help you get the best possible results when you try your new hair serum! 

  • A little goes a long way. Always, always start with less hair serum than you think you’ll need. These formulas are ultra-concentrated so you won’t need much. Start with one or two drops or pumps of your new serum and see how your hair responds. You can always add more if needed. Too much can make your hair look greasy or weighed down. 
  • Warm it up before applying. Hair serum’s viscosity and texture can be strange if you’ve never used this kind of product. Dispense the serum into your hands first and rub your palms together to warm it up before applying. This makes it a thinner consistency and easier to apply to your hair evenly. 
  • Avoid your roots (usually). Unless your hair is super coarse, you’ll want to apply hair serum from the midshaft down to the ends only. Avoid the roots if you have fine or medium textured hair. It’s easy for serum to make roots appear oily, but feel free to coat it all over your ends. 
  • Find the best time to apply. You can apply most hair serums when your hair is dry, damp, or sopping wet. You’ll need to do a little experimenting to find the best time to apply to your hair. We’ve found that applying hair serum to soaking wet curly or coily hair results in better defined curls. If you’re using your serum as a heat protectant, make sure you apply before using a flat iron, curling iron, or hair dryer. 
  • Don’t forget to clarify. Hair serum leaves a thin film on the hair, which is how it delivers the awesome benefits you’ll love. But that film doesn’t dissolve on its own and over time, it will build up on your hair. So don’t forget to use a clarifying shampoo or ACV rinse at least once a week to strip any remaining serum from your locks so you can start fresh.

We hope you aren’t still wondering, “what is hair serum?” But if you are, we suggest reading this guide again (it’s really good!). And while you’re here, be sure to check out our other hair care guides and see our favorite products.