Hair oil vs hair serum: what is the difference, and which goes on first?
Hair oil vs hair serum comes down to what they are made of. A hair oil is mostly plant oil, such as argan, jojoba or coconut oil, and it softens hair and adds shine. A hair serum is usually mostly silicones, which spread into a very thin layer on the hair surface that smooths it, keeps out humid air and helps protect it from heat.
So for frizz, humid weather and heat styling, a serum usually does more. For dry, coarse ends or a treatment before washing, an oil is often the better fit. Many products sold as hair oils are in fact a mix of both, and some are mostly silicone.
Hair oil vs hair serum: what is the difference?
| At a glance | Hair oil | Hair serum |
|---|---|---|
| Mostly made of | Plant oils such as argan, jojoba, coconut or olive oil, or mineral oil | Silicones, often with a little oil added |
| Feel | Richer, and oily if you use too much | Thin and silky, spreads very easily |
| Best at | Softening dry ends, adding shine, treatments before washing | Smoothing frizz, keeping out humid air, heat protection, shine |
| Suits | Thick, coarse, very dry or curly hair | Frizzy hair, humid weather, heat styling; light serums also suit fine hair |
| How to use | A few drops on the ends as a leave-in, or on dry hair before you wash it | A few drops on damp hair before drying, or on dry hair to smooth flyaways |
The line between oil and serum is blurry. Many serums contain some oil, and many hair oils are mostly silicone. The label tells you which one you are holding. EU rules require ingredients to be listed in order of weight, and only those under 1% may appear in any order at the end. If the list starts with names ending in -cone, -conol or -siloxane, the product is mainly silicone. If it starts with a plant oil, it is an oil.
What does a hair serum do?
Many smoothing serums combine 2 kinds of silicone. Volatile silicones, such as cyclopentasiloxane, spread the product and any oils in it thinly, then evaporate. Silicones such as dimethicone or dimethiconol stay on the hair as a very thin protective layer.
A 2025 review of silicones in hair care, written by dermatologists and published in Skin Appendage Disorders, lists what that layer does: less friction when you comb, less moisture loss, more shine, and a barrier against humidity that helps hair keep its style and minimises frizz. It also describes protection against heat damage. A 2015 review in the International Journal of Trichology adds that dimethicone, the most widely used silicone in hair care, repels water.
Shops sell the same idea under many names: anti-frizz serum, shine serum, hair fluid, liquid silk or liquid crystals.
Ellips capsules, often called hair oil capsules, sit on the serum side of the line. Each 1 ml capsule is a silicone serum with added plant ingredients, such as argan oil, jojoba oil or aloe vera, depending on the formula. That is why it smooths hair, calms frizz and protects from heat up to 220 °C when applied before styling.
One warning: not every product called a serum is for the lengths. Some are made for the scalp and are a different kind of product. If you are worried about shedding, see a doctor or dermatologist.
What does hair oil do?
A plant oil coats the hair, makes it softer and easier to comb, and adds shine. Many oils stay mostly on the surface, but not all. Laboratory studies in the Journal of Cosmetic Science found that coconut oil soaks into the hair while mineral oil does not, and that coconut oil reduced protein loss when used before and after washing. Sunflower oil and mineral oil did not.
Some oils also limit how much water hair takes up. Every wash makes hair swell and then shrink again as it dries. Researchers think this repeated swelling, called hygral fatigue, wears hair down over time, and one of those studies found that oil in the hair limited the swelling. That is the idea behind putting oil on dry hair before you wash it.
Which is better for frizz: oil or serum?
It depends on why your hair frizzes. If it frizzes in damp weather, a serum usually works better: silicones repel water, and the 2025 review describes them as a barrier against humidity.
If your hair frizzes because it is dry and rough, whatever the weather, start with conditioner and add a little oil. The American Academy of Dermatology suggests a bit of oil, such as argan oil, when hair still feels dry or frizzy after a leave-in conditioner.
Thick, frizzy hair often does best with both: a serum on damp hair before drying, and a drop of oil on the dry ends.
Which is better before heat styling?
A serum or a heat protectant. These usually rely on silicones, on polymers that form a protective layer, or on both. In a laboratory study in the Journal of Cosmetic Science, hair treated with such polymers before flat ironing broke significantly less when it was combed afterwards.
Whatever you use, check that the label states heat protection, and apply it before the heat, not after. Our article on why a straightener needs heat protection explains why the order matters.
Leave-in conditioner vs hair oil
A leave-in conditioner is the third option, and often the first one to try. It is a light, water-based cream or spray with conditioning ingredients that make hair easier to comb and reduce static.
The American Academy of Dermatology recommends leave-in conditioner for many hair types, from fine and limp to curly, dry, coloured and heat-styled hair. Its advice: use a small amount on towel-dried hair from the middle of the lengths to the ends, less for fine hair and more for thick hair, and keep it off the scalp, where it can build up and irritate.
In short: a leave-in conditioner for tangles and dryness, an oil or serum for shine, frizz and heat. If you use both, the conditioner goes on first.
Hair oil or serum first? How to layer them
The rule is simple: water-based products first, oil-based products last, and heat protection before any heat.
- Wash and condition. Squeeze your hair in a towel until it is damp, not dripping.
- Apply a leave-in conditioner, if you use one, to the lengths and ends.
- Apply serum or heat protectant to damp hair, before the hair dryer or any hot tool.
- Dry and style.
- Finish with a drop of oil on dry ends, only if they still look dry or frizzy.
Few people need every step. Fine hair usually needs one product. Thick, dry or curly hair may need 2 or 3. Our guide to the best hair oil for your hair type goes through each type.
Silicone serum or silicone-free?
Some people prefer silicone-free products, often for fine hair that goes flat easily or as part of a curly-hair routine. Others like the smoothness and frizz control that silicones give. Most silicones wash out with a regular shampoo. Heavier ones, such as dimethicone, can build up if you use a lot, and the 2025 review suggests a clarifying shampoo now and then, especially for fine or oily hair, while warning that using one too often can dry the hair. Choose what suits your hair.
If you want a pre-measured serum for after the shower, Ellips Hair Vitamin comes in single-use 1 ml capsules: one capsule per use, worked through damp lengths and ends, with no rinsing. It smooths hair, helps prevent split ends and breakage, and protects from heat up to 220 °C when applied before styling.
Frequently asked questions
Do you put hair oil or serum on first?
Serum first, oil last. Put the serum on damp hair before you dry it, so it is in your hair before the heat reaches it. Add oil at the end, on dry ends, only if they still look dry or frizzy. A leave-in conditioner goes on before both, because water-based products go on before oil-based ones.
Can you use hair oil and serum together?
Yes, if you use less of each and give them different jobs. The serum goes on damp hair before drying, for smoothness and heat protection. The oil goes on the dry ends afterwards, for softness and shine. Thick, dry or curly hair often likes both. Fine hair usually looks better with one, so drop the oil if your hair turns flat or greasy.
Do you need to rinse out hair serum?
No. Smoothing serums are leave-in products: you apply them to damp or dry hair and leave them in until your next wash. If you use a lot of a serum with heavier silicones such as dimethicone, a clarifying shampoo now and then clears any build-up. Serums made for the scalp are different products, so follow their own instructions.
Is hair serum good for fine hair?
Yes, if it is light and you use very little. Serums based on volatile silicones suit fine hair, because those silicones evaporate after you apply them. A 2025 dermatology review recommends volatile or water-soluble silicones for fine hair to keep its volume. Use a few drops on the ends and lower lengths only, and keep them away from the roots.
Is hair oil or serum better for dry hair?
Start with a rinse-out conditioner after every wash, because neither oil nor serum replaces it. Then choose by texture. Thick, coarse, dry hair often likes an oil on the ends. Dry hair that also frizzes or gets heat-styled does better with a serum on damp hair before drying. You can also use both: serum before drying, a drop of oil afterwards.