If you follow the rapper and songwriter Cardi B on Instagram, chances are you’ve seen her recent bombshell post about the importance of onion water for hair quality.

Furrowing your brow in confusion right now? Bear with me.

Cardi B, long-known as a beauty guru, recently posted the secret to her shiny, sleek hair: “My last 2 washes I been boiling onions and using the water to wash my hair … It’s odorless and I notice that it’s been giving a shine to my hair”.

Well, the proof is in the pudding. Cardi B posted a picture and video of her hair before and after she used the wash, and it’s decidedly smoother and shinier in the after the video.

So, how can you use this celebrity tip to boost your hair’s own shine and health? Below, I break down the truth behind applying onion juice (boiled onion water) to hair to boost shine — including a step-by-step protocol for trying this method at home.

In this article, you’ll learn:

• What onion water is. Onion water is a liquid created by boiling, soaking, blending, or juicing onions.
• Why onion water is beneficial for hair. Onion water can boost hair quality by reducing scalp inflammation, boosting keratin production, increasing scalp blood flow, and protecting the hair from environmental pollutants.
• Who should avoid onion water as a hair treatment. Those with an allergy to onions should naturally not use onion water as a hair treatment.
• How to make and use onion water: Onion water can be created by boiling, soaking, blending, or juicing. I provide step-by-step instructions for how to apply it as a treatment.
• Frequently asked questions about onion water for hair. From how to store it to how often it can be used as a treatment, I’ll answer all of your burning questions about onion water.

What Is Onion Water?

Onion water is simply water derived from boiling onions or pouring boiling water over onions. Some people make onion water by putting raw onions into a juicer or blending onions to create a paste.

Although Cardi B does not specify which type of onion is best for her special hair treatment, I advise using a plain yellow or white onion or any type of sweet onion (Mauis, Vidalias, or Walla Wallas). Green onions and shallots aren’t recommended for this use.

Benefits of Onion Water for Hair

Not everyone is a fan of eating onions — raw, boiled, or otherwise. (They’ve even been known to make some people cry). But that doesn’t mean this root vegetable isn’t worth benefitting from in other ways.

A member of the allium genus and rich in flavonoids and antioxidants, onions provide a range of internal health benefits — some of which can improve outside beauty too.

Onions are anti-fungal and anti-inflammatory. Onions are known to reduce inflammation, which can lead to much better hair growth. Inflammation of any kind in the body I known to deter both inward and outward signs of health.

They contain large quantities of quercetin. Quercetin is known to stimulate hair growth and has even helped some individuals who have alopecia.

The sulfur in onions helps with the production of keratin. You’ll notice “keratin” is in many haircare brand names, and it’s often listed as the active ingredient in hair products that work really well. Keratin is a protein that is found in your hair (and nails, organs, and other parts of the body). Boosting keratin means stimulated hair growth and overall healthier hair.

They can increase blood flow on the scalp. The high amount of flavonoids found in onions can boost hair growth because of the way flavonoids increase overall blood flow. When you have better blood flow on your scalp, hair grows faster and more easily.

Onions are loaded with vitamins. You’ll find high amounts of vitamins A and C in onions, both powerful nutrients for scalp health and environmental protection.

Hair Type Considerations

There is not currently data on how onion water affects various types of hair. Still, it should go without saying that if you have an allergy to onions or alliums of any kind, you must avoid onion water hair treatments. Otherwise, for the most part, I don’t advise anyone, in particular, to avoid this hair treatment as it is all-natural and overall safe.

If you do happen to be someone with an onion allergy but you’d like the benefits onion water can provide, I recommend trying OUAI Thick and Full Hair Supplements. These supplements have been highly reviewed by many hair experts and are great for hair health. They can also be a good option if you really don’t like the smell of onions.

How Do You Make Onion Water?

Various preparation methods and recipes can be used to create onion water. No matter what method you choose, I recommend starting with a white, yellow, or sweet onion (organic is preferable).

Method 1: Boiling

Clean and peel 3 to 4 onions, and drop them into 1 quart of water in a pot. Heat the pot over the stove until boiling, then turn down the heat to a simmer. Allow the pot to simmer for 15 to 20 minutes. Once cooled, transfer the water to a pitcher and refrigerate. Discard the onions.

Method 2: Soaking

Clean, peel, and rough chop 3 to 4 onions. Put the onions in a bowl filled with 1 quart of filtered water. Refrigerate for 12 hours. Drain the onion water into a pitcher and refrigerate. Discard the onions.

Method 3: Blending*

Blend 2 onions in a blender, along with enough filtered water to create a slurry-like liquid. Refrigerate.

Method 4: Juicing*

Juice 3 to 4 onions in a juicer. Add the juice to a pitcher and refrigerate.

* Blending and juicing will create a more potent onion liquid. This thicker onion juice stimulates the hair more and often delivers more benefits, but it’s also quite pungent. If you don’t like this strong smell, I recommend sticking to the boiling or soaking methods, which still provide numerous benefits.

How to Use Onion Water for Hair

I recommend applying onion juice to your hair once per week. Do this on a day when you are alone and have some time to relax and watch an episode of your favorite show or read a book for around an hour.

1. Start with dry hair. Put on an old shirt you don’t care about, and drape a bath towel around your shoulders.
2. Section most of your hair up in a clip, leaving about a two-inch section down.
3. Dip a cotton round or cotton ball into your onion water and saturate all of the scalp and follicles on the exposed area of the hair that is down. Don’t worry about the shafts and ends of the hair just yet.
4. Now, let down another 2-inch “band” of hair around your head, and clip the rest up.
5. Saturate these exposed roots and the scalp in the same manner.
6. Repeat the above steps until all of your scalp has been saturated with onion water. If you feel like adding a bit of olive or jojoba oil to the ends of your hair for added moisture, now is the time.
7. With the rest of the onion water you have left, lean over your sink or shower and pour it on all of your hair, from roots to ends. Try to get every strand covered.
8. If the onion water is saturating your hair so much that it is dripping wet, lightly squeeze your hair so that it’s still wet but not soaking and dripping all over.
9. Now, wrap your hair in a towel (do not dry; just wrap). Or, use plastic wrap if you don’t want the onion water to get on your towels.
10. Wait 1 hour, then get in the shower and rinse all of your hair for several minutes, massaging your scalp as you do so.
11. After all of the onion water has been rinsed out, wash your hair with a mild shampoo, rinse, condition, and rinse again. Style as usual.

FAQ Section

How often should you use onion water?

It’s best to use onion water as a hair treatment once per week. If it’s easier for your schedule, use it as an overnight treatment by applying the onion water, then putting on a soft waterproof cap and rinsing in the morning.

How long does it take onion water to grow hair?

Onion water should start to strengthen hair and improve elasticity and shine in three to four weeks. If you stop using the treatment at any time after that, you may lose your results.

Why is onion water not working on my hair?

Not everyone will benefit from onion water as a hair treatment. Those who have had their hair fall out after at-home hair treatments or those with more serious hair issues, such as alopecia, should seek professional intervention.

Can I store onion juice for hair in the fridge?

Yes, you can store onion water for several days up to a week. Any longer than this and the beneficial properties of the onions may deteriorate.

Is rice water better than onion juice for hair growth?

Both rice water and onion juice have been known to promote healthier hair and hair growth. To find what works best for you, try both methods for at least three to four weeks each.

Can using onion water for hair cause dandruff?

If anything, onion water should help get rid of dandruff. If your onion water hair treatment is causing dandruff (rare), cease using this treatment immediately.