Hair Oil vs. Hair Serum: What's the Difference?

As beauty editors, you don't have to tell us twice that you feel overwhelmed by the amount of products on offer. And while adding a new buzzy ingredient into your routine may keep you from experiencing FOMO, it might not be what you really need. Our advice? Simplify your routine—especially when it comes to hair. For instance, do you really need a hair oil and a hair serum? Maybe not.

The major difference is the products' ability to penetrate the hair strand. Oils tend to be absorbed by the hair, while serums typically feel like they're coating strands. "Hair oil conditions and nourishes hair, directly impacting overall hair health, but no such impact is seen with the use of hair serums, says Deaundra Metzger, an Atlanta-based celebrity hairstylist. "Hair oil penetrates deep into the hair shaft to nourish hair from within, whereas hair serum merely sits on the surface and forms a layer."

It's best to think of a hair serum as a shield or armor for the hair. If you're styling your hair with hot tools, Isfahan Chambers-Harris, a trichologist, Ph.D. Scientist, and founder Alodia Haircare, suggests prepping hair with a silicone-based serum for heat protection.

What Is Hair Oil?

As the name implies, hair oil is an oil-based product. According to Dr. Chambers-Harris, the formula typically consists of at least two carrier oils (like avocado, coconut, and almond) and essential oils (like lavender and lemongrass).

An oil offers a handful of benefits for the hair and scalp, including scalp stimulation, maintaining moisture within the strand, and aiding in length retention. In turn, the oil can help hair feel softer and appear shinier.

All hair types and textures can use a hair oil, but how you use it will vary. "Drier hair types such as textured hair tolerate oils well," Dr. Chambers-Harris says. "Straighter hair types can use oils but should use them before shampooing." Rinsing the oil out with shampoo will still deliver the benefits without weighing down straight and/or fine hair.

What Is Hair Serum?

Hair serum is a lightweight product that covers the outer surface of the hair, acting as a seal or protectant. Hair serums typically contain silicones or silicone-like substances that sit on top of the hair strand, Dr. Chambers-Harris tells us.

"Hair serums have benefits such as taming frizz and flyaways, adding shine, shielding against humidity, softening your strands, and helping with damage caused by chemically damaged hair or hair that has been over-styled with heat tools," shares Metzger.

Tips

They're also a universal product, however, if you're prone to frizz or have chemically-treated hair, you can especially benefit from adding a hair serum to your routine. Just be aware of the ingredients, specifically if you have curly/textured hair.

"If you are wearing your hair in its curly/textured state most of the time, you should be careful with using silicone-based serums because they can cause buildup over time and block moisture from getting in, leaving your hair feeling and looking dry—particularly if you are using a non-sulfate shampoo to wash your hair," explains Dr. Chambers-Harris.

The Best Way to Use Hair Oils

There are a number of ways to use hair oil in your routine based on your hair type and its needs. "You can oil the hair and scalp before shampoo. You can use it as a hot oil conditioning treatment. And you can use them as a 'sealant' to seal in the cream-based hair conditioner that you used for styling," says Dr. Chambers-Harris.

How much product you use will vary by hair length. "If you're rocking a shorter style, then one to two small pumps are enough, while longer styles may find three to four pumps more appropriate," says Metzger. Again, it's important to note that if you have straight hair, oil is best used as a pre-shampoo treatment to prevent weighing hair down.

The Best Way to Use Hair Serums

As for hair serums, when you use one in your routine will depend on its purpose. When you're applying it, Metzger suggests going by hair length. "A single pump of serum will suffice for mid-length hair, while long hair may require a bit more," the stylist says.

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