Most advice on this lands on "two to three times a week" and leaves it there. That number is useless on its own, because how often you should oil depends on three things: how thick your individual strands are, how porous they are, and how often you wash.
Here is how to work out your own answer.
Start with strand thickness
This is about the width of a single hair, not how much hair you have.
| Hair type | Starting frequency | Where to apply |
|---|---|---|
| Fine | Once a week | Ends only |
| Medium | Two to three times a week | Mid-lengths and ends |
| Coarse or coily | Three to four times a week, or daily on ends | Mid-lengths, ends, and scalp if it feels dry |
Fine hair has the least surface area per strand and the least room for product before it goes flat. Coarse and coily hair loses moisture faster along the strand, particularly where the hair bends, and tolerates far more.
Then adjust for porosity
Porosity is how readily your cuticle lets moisture in and out. The float test is rough but useful: drop a clean, dry shed hair into a glass of water and leave it a few minutes.
- Floats — low porosity. The cuticle lies flat. Oil sits on the surface and builds up quickly. Use less, less often, and apply to damp hair so it has something to seal in.
- Sinks slowly — medium porosity. The table above works as written.
- Sinks fast — high porosity. The cuticle is raised, often from colour, heat or age. Oil absorbs quickly and disappears. Increase frequency by roughly one application a week.
Then adjust for wash frequency
This is the one people skip, and it is where most buildup comes from.
Oil accumulates. If you apply three times a week and wash once, you are removing one layer and adding three. Within a month hair feels heavy, dull and coated — and the usual response is to blame the oil rather than the ratio.
A simple rule: do not apply oil more than twice between washes. Wash twice a week, and up to four applications is fine. Wash once a week, and stay at two.
If you want to oil more often than that, wash more often. A water-activated powder shampoo makes that easier — it cleanses without the stripping feeling that pushes people toward washing less in the first place.
Scalp and lengths are different schedules
The ends of your hair are the oldest part, often two or three years old, and have been through every wash, brush and heat exposure since. They need the most.
The scalp produces its own oil. Adding more is only worth it if it genuinely feels tight or dry, and even then it wants a light hand and a wash reasonably soon after.
A workable default: ends every time, mid-lengths most times, scalp rarely.
How to tell you have got it wrong
Too often — hair looks flat at the root within a day of washing, feels coated rather than soft, clumps into separated strands, and shampoo struggles to lather.
Not often enough — ends feel rough and look dull, more flyaways, tangling that was not there before, and small white specks along the strand where hair has snapped.
Adjust by one application a week and give it two weeks before judging. Hair responds slowly.
Concentration changes the maths
A heavier oil applied lightly and a light oil applied generously are not the same thing. Concentrated formulas need less per application, which means less accumulation between washes and more room in your schedule.
Illuminous is a waterless concentrate — six to seven drops does what ten to fifteen drops of a traditional oil would, so it works on damp or dry hair without the weight that forces you to wash sooner.
Common questions
Can I oil every day?
On the ends, if your hair is coarse or coily and you wash at least twice a week, yes. On fine hair, no.
Overnight or before washing?
Both work. Overnight gives longer contact time; pre-wash is more forgiving if you are still finding your amount.
Does hair get used to oil and stop responding?
No — that is buildup changing how the oil behaves, not tolerance. We covered why in does your hair get used to products.
Should I change frequency in winter?
Usually yes. Indoor heating and cold air both pull moisture from hair. One extra application a week is a reasonable adjustment.
Next: how much hair oil to use and whether to apply it to wet or dry hair.
