How to Use Hair Oils and Serums Without Weighing Hair Down

Hair oil and hair serum may share the same bathroom shelf, but while one is a treatment the other is a finish.

A hair serum is typically the last step, used to smooth the lengths, tame frizz and flyaways, and give the hair a polished shine. It is particularly useful in weather like ours, when hair can quickly lose its sleekness to humidity.

Hair oil, meanwhile, is about conditioning. Washing our hair can strip its natural oils, so coating the lengths with hair oil before can help protect them.

The two aren't mutually exclusive. Oil can be used as a pre-shampoo treatment, followed by a small amount of serum to finish. But for fine hair or strands prone to falling flat, layering both can easily tip from polished to weighed down.

Hair serum can transform your hair, lending it a frizz-free, high-shine finish. But it can just as easily leave it looking limp and grease-coated. So if you are wondering how to use hair serum, the trick is knowing how much to use, where to put it and when to apply it.

Generally speaking, serum belongs on the mid-lengths and ends, rather than the scalp. "The best way to ensure even distribution is to start by dividing the hair into four sections and applying a tiny amount of serum to each section individually," says Vijai Vadivu Rangasamy, Curly Hair Specialist, Hair Care Formulator & Founder and CEO, The Curl Nation.

You can apply it on damp hair to smooth the strands; on dry hair, it can act as a finishing touch. On wet hair, "use a raking motion with your fingers to work the product through the lengths and on dry hair, the praying hands method works best—gently smoothing the product over," she adds. The goal is to enhance shine—not hair that looks like a batch of fresh fries.

For that, the Nexxus Promend Oil Resurrection Hair Serum is a good option. Enriched with keratin, collagen and elastin, it is designed to help replenish damaged hair, while its oils help smooth and condition the strands.

For a budget buy, look at the Dove Peptide Bond Strength Bi-Phasic Oil+Serum. The blend is infused with 15% protein peptide complex to reduce frizz, roughness, and dryness.

Sometimes the best beauty tricks are also the simplest, and oiling your hair is one of them. Surely our grandmothers and mothers knew this when they made Sunday champis mandatory. The most important hair oiling tips? Knowing how much is enough. Oil is concentrated, so you don't need much of it. Where you apply it and how long you leave it on is key.

If your lengths and ends feel dry, concentrate the oil there rather than applying it all over. Oiling the scalp is part of a traditional champi, but if your scalp is naturally oily or prone to buildup, adding more oil can leave it feeling greasier.

As for how to use hair oil, "even 1–3 drops can be enough," states Rangasamy. And contrary to popular belief, you don't necessarily need to leave oil on overnight. "I generally recommend leaving it on for around 20–30 minutes," says Dr. Geeta Mehra Fazalbhoy, Founder, Skin & You Clinic. "More oil, longer oiling and overnight oiling do not necessarily mean more hair growth or a healthier scalp."

Remember, one person's glossy locks may be another's super-greasy hair day, so know your hair type before you squeeze out more product.

The right quantity usually depends on your hair's length, density and texture, as well as the formula. For those looking for a hair serum for fine hair, Rangasamy recommends a lightweight, water-based formula. "I prefer hydrating ingredients such as glycerin or hyaluronic acid," she says. "Avoid serums that are oil-based or contain silicones, butters or other buildup causing ingredients."

Fine hair can be easily weighed down, so start with a tiny amount and keep heavier products away from the roots. The same applies when choosing a hair oil for fine hair—a little can go a long way.

Thick or coarse hair may tolerate more product, particularly through dry lengths and ends. Concentrate product where the hair feels driest rather than coating the entire head.

Oily roots and dry lengths? "Treat the scalp and hair lengths as two different environments," says Dr. Fazalbhoy. "Keep the scalp clean and focus the conditioner and serum on the mid-lengths and ends."

The most common mistake is using too much product and uneven distribution leading to greasy patches. "Emulsifying it in your palm first helps distribute a smaller amount more evenly," says Rangasamy, who also advises against repeatedly adding serum or oil to control dryness and frizz. "If you constantly feel the need to add more product, it's worth addressing the actual hair issue—whether it's lack of moisture, damage, or buildup—rather than continuing to layer more product."

Likewise, oil, serum, leave-in conditioner, and styling products all have a place in a routine. Using several rich products together can weigh down hair. As can using them directly on your roots.

But how do you know when you've gone too far? "Signs include greasy or heavy-looking hair, loss of volume, itching, flaking, scalp odour and difficulty getting the hair clean," says Dr. Fazalbhoy.

How many of us have walked out with greasy hair even after a hair wash? I certainly have. And if you have too, you may need to rethink how you're shampooing.

"When washing, concentrate shampoo on the scalp, where sebum, sweat, and product accumulate," says Dr. Fazalbhoy. "Aggressive shampooing can increase dryness."

Should you double shampoo? "If you've applied a small amount of oil, one thorough shampoo may be sufficient," suggests Dr. Fazalbhoy. "If the hair still feels greasy after the first wash, a second gentle shampoo can be used. The important point is to cleanse the scalp adequately without repeatedly stripping the lengths."

And please don't skip the conditioner. If your lengths are dry or you've shampooed more than once, conditioner can help restore softness and manageability.

You know Day 3 hair—when it isn't quite ready for a wash but could use a little refresh? It's dry shampoo on the roots and a touch of serum to the rescue. A serum, like the Love Beauty Planet Argan Oil & Lavender Hair Serum, is designed to control frizz and lend a glossy finish to liven the hair.

It can put off washing your hair for another day, but if your roots are visibly oily or your hair has started to feel coated, no amount of serum is going to make it feel fresh—only a wash can.

Just like with your skin, not all greasy-looking hair is from using too much product. An oily scalp is a hair characteristic and doesn't need to be "corrected". "Sebum production is largely determined by individual biology, hormones, genetics and age," says Dr. Fazalbhoy. "Deliberately avoiding shampooing for prolonged periods does not reliably 'train' the scalp to stop producing oil."

If your roots are naturally oily, keep heavier oils and serums away from the scalp. And if your roots feel oily, wash them rather than disguising them with more product.

The best way to use hair oil or serum isn't to use too much or avoid them altogether. It is to understand what your hair needs.

Start with less, apply product where it's needed and adjust according to your hair's texture, density and scalp. Fine hair? Use a tiny amount. Oily roots? Keep heavier products away from the scalp. Dry ends? Concentrate product there. Want shine? Serum may be enough. Naturally oily hair? You don't need to fix it.

When it comes to hair oil and serum, the best routine is the one that gives you the result you want.