How to use hair oil: wet or dry hair, how much and how often
How to use hair oil, in short: rub a small amount between your palms and smooth it through the lengths and ends of damp, towel-dried hair, away from the roots. Then dry and style as usual, with no rinsing. On dry hair, use even less, just enough to smooth flyaways and frizzy ends.
What does hair oil do to your hair?
Hair oil works on the surface of the hair. It coats the outer layer, so hairs rub less against each other and against your brush. That is why oiled hair looks shinier, feels softer and is easier to comb.
Oil does not add water to hair. It slows water down. In a 2007 laboratory study in the Journal of Cosmetic Science, oil-treated hair took up less moisture from the air. Water also moved in and out of it more slowly. The researchers compared this to moisturising, because the oil also slows water loss. That matters: a 2015 review in the International Journal of Trichology names repeated swelling and drying as a cause of wear.
Some oils also sink partly into the hair. In a 2003 study, coconut oil was the only oil of the 3 tested that reduced protein loss from hair, both when used before washing and after it. Sunflower oil and mineral oil did not.
What oil cannot do is mend damage. Hair is not alive, so it cannot heal, and oil on the lengths does nothing at the roots.
Should you put hair oil on wet or dry hair?
Both work, but they do different jobs. Damp hair after washing is the main moment: the oil spreads thinly and evenly, and it is in place before you dry and style. Dry hair needs much less, just enough to smooth the ends. Avoid dripping-wet hair, where the water stops the oil from spreading. Squeeze your hair in a towel first.
| When | What it does | How much |
|---|---|---|
| Damp hair, after washing | Conditions the lengths and ends, makes hair easier to comb and is in place before heat | Your usual amount |
| Dry hair, between washes | Smooths flyaways and frizzy ends and adds shine | A little, on the ends only |
| Before washing | Can reduce protein loss from the hair (shown with coconut oil) | More, then shampoo it out |
A treatment before washing is optional. If you try it, put the oil on dry lengths, leave it on for a while or overnight, then shampoo as usual. You may need to shampoo twice.
How to use hair oil in 6 steps
These steps follow the American Academy of Dermatology (AAD) rules for leave-in conditioners, which suit a leave-in oil just as well.
- Wash and condition as usual. Rinse the conditioner out well.
- Squeeze, do not rub. Wrap your hair in a towel to soak up the water, as the AAD advises. Leave it a bit damp.
- Spread the oil on your palms. Rub your hands together so the oil coats both palms evenly.
- Start at the ends. The ends are the oldest, most worn part of your hair, so they need oil most. Work up to the middle of the lengths and stop well before the roots.
- Comb gently. A wide-tooth comb spreads the oil evenly. Wet hair breaks more easily, so the AAD suggests letting straight hair dry a little before combing. For tightly curled or coily hair, it suggests the opposite: comb it while wet, when it breaks less.
- Dry and style. Let your hair dry partly on its own, then blow-dry or style as usual.
Hair oil on the ends also helps prevent them from splitting. Here is more on what causes split ends and how to prevent them.
How much hair oil should you use?
Less than you think. The AAD's advice for leave-in conditioner is to use the smallest amount that does the job, so hair does not look greasy. Studies in the Journal of Cosmetic Science explain why. With many oils, a thin layer is partly absorbed by the hair over time. A thick layer stays on the surface, where it looks oily and weighs hair down.
- Fine or short hair: a few drops, on the ends only.
- Medium hair: enough to coat both palms lightly.
- Thick, long or curly hair: a little more, added in small amounts to the driest parts.
You can always add a drop if your ends still feel dry, but you cannot take oil back out without washing.
With a bottle, the amount is a guess. A measured dose takes the guessing away: Ellips Hair Vitamin comes in single-use 1 ml capsules, enough for the lengths and ends. For very fine hair, use half a capsule on the ends only. Twist the tip off, or snip it with small scissors if the capsule has gone hard in the cold.
Hair oil before or after blow-drying?
Before, if you want protection. After, if you only want shine. Many people do both: their usual amount on damp hair, then a trace on the dry ends.
Oil before heat only protects if the product is made for it. A plain kitchen oil or a single-ingredient oil is usually not made or tested as a heat protector. The 2015 review recommends a silicone-based heat protector for dryers and straighteners, because silicones spread the heat along the hair surface. It also warns that oily products can make heat-damaged hair feel easier to comb, until the next wash shows the damage. So choose a product that states heat protection and a temperature, and put it on before the heat.
How you dry matters too. In a 2011 study in the Annals of Dermatology, damage to the hair surface rose with the dryer's temperature. A dryer held about 15 cm away and kept moving did less damage overall than letting hair dry on its own.
With a straightener, the order is the same. The AAD advises straightening only dry hair, on a low or medium setting, no more often than every other day. Here is why heat protection has to be in your hair before the straightener closes.
How often should you use hair oil?
As often as your ends need it. For most people that means after each wash, plus a little on dry ends in between if they look frizzy. Daily use is fine as long as your hair does not start to feel heavy.
Watch for build-up. If your hair feels coated, looks flat or will not hold a style, use less or wash more often. The AAD says leave-in conditioner on the middle and ends of the hair can stay in for up to a week. After that, wash it out with shampoo and water.
How to use hair oil without greasy hair
- Keep it off the roots and scalp. Your scalp makes its own oil, and the AAD notes that leave-in conditioner on the scalp can build up and irritate it.
- Spread it on your palms first, so it goes on as a thin layer.
- Use it on damp hair, where it spreads thinner and more evenly.
- Go lighter on fine, straight or untreated hair. The 2015 review notes that leave-on products can make straight, untreated hair look oily and dull.
- Keep your hands out of your hair during the day. Fingers carry oil to the roots.
3 hair oil myths worth dropping
"Oil moisturises hair." Only in a limited sense. Oil contains no water; it slows water loss. Dry hair still needs conditioner after every wash, as the AAD recommends.
"Any oil protects from heat." Only products made and tested for heat protection do, and only when they go on before the heat.
"Oiling the scalp stops shedding." No hair oil changes how much hair you shed. A 2022 review of hair oils in the International Journal of Trichology found many popular claims about them exaggerated and poorly backed by studies. If you shed more than usual, see a doctor or dermatologist.
The short version
Damp hair, a small amount, lengths and ends, never the roots, and before any heat. If you want the amount measured for you and heat protection up to 220 °C when applied before styling, Ellips leave-in hair oil capsules are an option. They are silicone-based, the plant oils differ by formula, and they contain soybean oil, so skip them if you are allergic to soy. Good habits matter more than any bottle.
Frequently asked questions
Can you leave hair oil in overnight?
Yes, on the lengths and ends. A leave-in oil is made to stay in. The American Academy of Dermatology says even leave-in conditioner can stay on the middle and ends of the hair for up to a week before you wash it out. For an overnight treatment before washing, use more oil, tie your hair loosely and cover your pillow. If your scalp is flaky or itchy, ask a dermatologist before oiling it.
Does hair oil protect hair from heat?
Only if it is made for it. A plain oil is usually not made or tested as a heat protector, and oily products can make heat-damaged hair feel smoother until the next wash shows the damage. Choose a product that states heat protection and a temperature, put it on before the hair dryer or straightener, and use the lowest heat setting that works for your hair.
Should you put hair oil on your scalp?
This guide is about the lengths and ends, where hair needs oil most. Oiling the scalp is a separate habit, and a 2022 review of hair oils found that many claims made for them are exaggerated. Oil on the scalp can also make your roots look greasy. If your scalp is flaky, itchy or sore, see a pharmacist or dermatologist instead of adding oil.
Hair oil or leave-in conditioner first?
Leave-in conditioner first, oil last. Most leave-in conditioners and heat sprays are water-based, so they go on damp hair straight after washing. The oil goes on top, to smooth the hair surface and slow the loss of moisture. If your oil already states heat protection, you may not need a separate heat spray as well.