What a pre-wash treatment is
A pre-wash treatment is oil applied to dry hair, and sometimes the scalp, before shampooing. It is left on for a while, from a few minutes to several hours, then washed out. The goal is to cushion the hair during washing, so that it loses less of its natural oil and feels softer afterward. Hair oiling in this way has a long tradition in several cultures, and it is practiced for both hair feel and routine.
The expectations should stay modest. Oil is a cosmetic aid. It can make hair feel softer and look glossier, and it may reduce the roughness shampoo causes. It does not change hair structure permanently, repair split ends or guarantee growth, and evidence for many popular claims is limited.
Comparing common oils
The differences are mostly about weight, feel and how easily each rinses out.
- Coconut oil. The best-known pre-wash oil. Some limited research is often cited as suggesting that it reduces protein loss from hair during washing more than some other oils, but studies are small and results differ between people. It is solid at cooler room temperatures and can feel heavy. Some people, especially with fine hair or protein-sensitive hair, find it leaves hair stiff or tangled.
- Olive oil. Thicker and richer, with a stronger scent. Often favored for thick or coarse hair and sometimes takes several washes to remove completely.
- Castor oil. Very thick and sticky. Typically used mixed with a lighter oil rather than alone, because it is hard to spread and hard to wash out.
- Jojoba oil. Light, with a texture that many describe as similar to scalp oils. A good choice for fine hair and for those who dislike greasiness.
- Sweet almond oil. Light to medium and easy to spread; avoid it if you have a nut allergy.
- Argan oil. Light and silky, often used on ends. It tends to be more expensive.
- Sesame oil. Traditional in some regions, with a distinct scent. Sesame is a recognized allergen for some people.
- Avocado oil. Rich but relatively easy to spread.
No oil is clearly “best”. Fine, straight hair generally prefers lighter oils in small amounts. Thick, curly or coarse hair often tolerates, and sometimes needs, richer oils. Color-treated or heat-damaged hair is often dry and may benefit, but the same reasoning applies.
How to apply
- Start with dry or slightly damp hair, gently detangled.
- Warm a small amount of oil between your palms. Do not heat it hot, and avoid microwaving it; test on your wrist first. Some people warm the container in a bowl of warm water.
- Smooth it through the lengths and ends first. Fine hair may need only a teaspoon or so; longer, thicker hair uses more.
- If you apply to the scalp, use fingertips and keep it light, as covered in the section on scalp care.
- Leave it for 30 minutes to a few hours. Overnight is common in some traditions, but oil on pillowcases and the extra time on the scalp is not always welcome, and for people prone to clogged follicles or flakes, shorter is wiser.
- Wash with shampoo, applying it to the oily hair first before adding water. Many people find oil rinses out more easily this way. A second wash may be needed.
Washing the oil out
This is where most people struggle. Heavy oils on fine hair can leave residue that looks limp. Tips:
- Apply shampoo to dry, oiled hair, then add a little water to lather.
- Use warm, not hot, water.
- Lather twice if needed, rather than more shampoo on the first round.
- If you use a handmade cleansing bar, remember it is not the same as a formulated shampoo, and shampoo bars may behave differently with oily hair.
Who may want to skip it
- Oily or flaky scalps. Extra oil may worsen buildup or flaking in some people. Flakes can have several causes, so a persistent problem should be looked at by a doctor or dermatologist rather than treated with more oil.
- Anyone with a known allergy to nut or seed oils.
- Anyone with a sensitive or irritated scalp. Always patch test an oil on a small patch of skin first.
- People who are pregnant or nursing should be cautious with essential oils in the mix. Plain carrier oils are generally less of a concern.
- Very fine hair that goes limp easily.
Adding scent or essential oils
Rosemary, lavender and peppermint essential oils are often added to hair oils. Evidence for benefits such as growth is limited, and they can irritate the scalp or trigger allergies. If you add any, essential oil dilution is important, and the amount must be low. Citrus oils may increase sun sensitivity. Take extra care around pets and young children, who can be more sensitive to strong scent. Plain oil is perfectly fine.
Storage and freshness
Oils can go rancid. Keep them in a cool, dark place with the lid closed, and toss anything that smells sharp, like old paint or crayons. Different oils last different lengths of time, and oil shelf life is something worth checking before you mix a large batch. A small bottle you finish in a few months is usually better than a large one that sits. Do not add water, aloe or herbal infusions to an oil blend, since that makes it perishable.
Putting it together
If you want to try it, pick one light oil, apply a small amount before washing once a week, and keep notes. Watch how your hair and scalp behave across a few washes. If hair feels greasy, heavy or itchy, use less, switch oils or drop the step. For some people, the best result is simply a more relaxed wash day.