Onion Oil for Hair Growth: Benefits, How to Use It and What to Expect

Onion oil is used as a pre-wash scalp treatment, usually once or twice a week. You apply it to the scalp, massage it in, leave it for a short time, then wash it out well before your normal routine.

People try it hoping for fuller-looking hair, and onions do have a sensible link to hair: they are rich in sulfur, a building block of hair. The evidence, however, is limited, so this guide keeps the claims honest.

What onion oil is claimed to do

Onions are rich in sulfur, and sulfur is part of the structure of hair itself. That is the main reason onion preparations became popular for hair care.

In practice, onion oil is best thought of as a scalp and hair treatment that can leave hair feeling conditioned and looked after, rather than a proven growth treatment. Like other hair growth oils, it supports the condition of the hair you have.

What the evidence actually says

A small 2002 study tested onion juice, not shop-bought oil, on patchy hair loss known as alopecia areata. Some people in that study saw regrowth with the juice.

That distinction matters: fresh onion juice and a commercial onion oil are different products, with different strengths and ingredients. The study was small, it was about a specific patchy condition, and it was not a test of bottled onion oil for general thinning.

Treat the evidence as limited and interesting, not as proof that onion oil regrows hair.

	Fresh onion juice	Shop-bought onion oil
What it is	Juice strained from a fresh onion, usually mixed with a carrier oil at home	A ready-made oil with onion in a base oil
Evidence	Used in the small 2002 study on patchy hair loss	Not what the study tested, so its results cannot simply be transferred
Smell	The strongest; fades with a thorough wash	Usually milder, and often scented
Convenience	Must be made fresh each time	Ready to use, one to two times a week

The often-quoted onion juice study involved people with alopecia areata, an autoimmune condition that causes round bald patches, not common pattern thinning. DermNet explains that alopecia areata can regrow on its own and often needs medical treatment, so results from that small study cannot be applied to everyone. The American Academy of Dermatology and the NHS both describe the main types of hair loss.

How to use onion oil, step by step

Using a pre-made onion oil

Start with dry or slightly damp hair. Part your hair, apply a small amount of oil directly to the scalp in sections, and massage gently with your fingertips for a few minutes.

Leave it on for 30 minutes to an hour, then shampoo thoroughly and condition as usual. Use it one to two times a week as a pre-wash treatment.

A simple homemade version

To make a basic version at home, blend or grate a small onion, strain the juice through a clean cloth, and mix that juice with a spoonful of a plain carrier oil such as coconut oil. Use it straight away, apply it to the scalp in the same way as above, and wash it out well.

Make a fresh batch each time rather than storing it.

If you prefer a scented option and a simpler routine, you may find our guide to using rosemary oil correctly easier to stick with.

Choosing between homemade and shop-bought

The homemade version gives you a fresh batch and a short ingredient list that you control completely. The trade-offs are effort and smell: it takes grating and straining each time, and the scent is at its strongest.

A shop-bought oil is the low-effort option, with a milder smell and a consistent strength from bottle to bottle. If you buy one, check the ingredients: onion should feature clearly, and if your scalp is sensitive, avoid heavily fragranced versions.

If you want an option with a slightly stronger evidence base, read our guide to rosemary oil for hair.

A simple weekly routine with onion oil

Pick one or two wash days a week and apply the oil 30 to 60 minutes before you wash. Keeping it tied to wash days makes the routine easy to remember and keeps the smell manageable.

On non-treatment days, carry on with your normal washing and conditioning. Onion oil is an extra step in a basic routine, not a replacement for it, and basic care does most of the everyday work of keeping hair in good condition.

Give the routine a fair trial of a few months before you judge it. Changing products every week tells you nothing about any of them.

How to reduce the smell

The smell is the main reason people give up on onion oil, but it is manageable.

• Rinse well and shampoo carefully, focusing on the scalp.
• Add a drop of a pleasant essential oil to the mixture before applying it.
• Do not leave it on overnight if the smell bothers you; a shorter pre-wash treatment is fine.
• Rinse with plenty of water before you condition.

If a scent lingers anywhere, it is usually on fabrics rather than on washed hair. Washing your pillowcase and rinsing your brush after treatment days deals with most of it.

Safety notes and patch test

Onion can irritate sensitive skin. Always do a patch test first: dab a little of the oil or mixture behind your ear or on your inner elbow, wait 24 hours, and check for redness, itching or burning.

Do not use it on broken or sore skin, keep it out of your eyes, and stop using it if irritation continues. If you make the homemade version, be extra careful when straining and applying it near your eyes, as fresh onion juice stings.

What to expect, honestly

Oils support hair and scalp care and appearance. They do not cure baldness or guarantee regrowth.

Onion oil may help your hair feel softer and break less, so it can keep its length better, but any visible change takes months of consistent use. If your hair loss is patchy, sudden or spreading, see a doctor: patchy loss in particular deserves a proper diagnosis rather than home treatment alone.

Frequently asked questions

How often should I use onion oil?

Once or twice a week, before washing, is plenty for most people.

Is onion oil the same as onion juice?

No. The small 2002 study used fresh onion juice. Bottled oils are different products, so its results cannot simply be transferred to them.

Will it make my hair smell?

A thorough wash removes most of the smell. The tips above help if any scent lingers.

Can I mix onion oil with other oils?

Yes: the homemade version is mixed with a carrier oil such as coconut, and pre-made oils are blends already. Keep the onion part modest, and patch test any new mixture before you use it on your whole scalp.

Key takeaways

• Onions provide sulfur, a building block of hair, but evidence for onion oil is limited.
• Apply to the scalp, leave 30 to 60 minutes, wash out well, one to two times a week.
• Patch test first, because onion can irritate sensitive skin.
• Expect better-feeling hair over time, not guaranteed regrowth.

Keep reading: Rosemary Oil for Hair Growth: How to Use It Correctly and Homemade Hair Growth Oil Recipe with Coconut, Curry Leaves and Fenugreek.

This article is general information only and is not medical advice. Please consult a healthcare professional for personal advice.