For many, watching their hair thin or fall out can feel deeply personal and overwhelming. The emotional toll of seeing once-thick, healthy locks diminish is often paired with the frustration of trying product after product, only to be left disappointed. If you’ve tried over-the-counter remedies like minoxidil but ended up with irritated skin or underwhelming results, you’re not alone. That’s why so many are seeking natural, effective alternatives.
One such solution is onion juice. Yes, the very onions you chop up for your meals, the ones that bring tears to your eyes. This unassuming kitchen staple is gaining significant attention for its impressive ability to promote hair growth. While onions have long been recognized in traditional medicine for their sulfur-rich composition, modern research is beginning to reveal their complex nutritional profile—many of which are already associated with hair follicle health, scalp circulation, and reduced oxidative stress.
Now, I get it—onion juice might not sound like your typical hair care miracle, and let’s be honest, the smell isn’t exactly a spa treatment. But here’s the thing, the science behind it is compelling. With the right approach, onion juice could be the affordable, natural, and effective remedy you’ve been searching for.
In this article, we’ll break down the chemical properties of different Allium cepa varieties, highlighting the key nutrients that may contribute to stronger, healthier, and fuller hair. We’ll also explore how to use onion-based treatments effectively, and integrate this affordable, natural approach into your hair care routine.
Let’s get started on your journey to fuller, stronger, and more vibrant hair!
The Science-Backed Benefits of Onion Extract
Onions (Allium cepa) have long been valued for more than just their culinary uses. Rich in flavonoids, sulfur compounds, vitamins, and minerals, these powerhouse ingredients provide an impressive array of health benefits. They support the immune system and offer antioxidant protection [4], promote heart health and help regulate blood pressure [2], possess anti-inflammatory properties [4], and exhibit antimicrobial effects [10]. Additionally, they contribute to skin and wound healing [8] and aid in gut health and digestion [1].
While these well-known benefits make onions a powerhouse ingredient for overall wellness, recent research has turned the spotlight onto their potential to promote hair growth. The same bioactive compounds that enhance immune function and reduce inflammation may also play a role in stimulating hair follicles, strengthening strands, and reducing hair loss.
Key Compounds in Onion Juice and Their Role in Hair Growth
The hair-enhancing properties of onion juice are attributed to several bioactive compounds, each playing a vital role in maintaining scalp health and follicle strength:
✅ Sulfur
The Role of Sulfur in Promoting Hair Growth
🧅 Keratin Formation & Structural Integrity
Sulfur-containing amino acids, methionine and cysteine, are primary building blocks of keratin, which accounts for 80–90% of the hair’s structure [17]. These amino acids are responsible for forming disulfide bonds, which provide hair elasticity, resilience, and tensile strength, preventing it from becoming weak and brittle.
🧅 Strengthens Hair Bonds & Reduces Breakage
Hair structure is maintained by three main types of bonds: hydrogen bonds, ionic bonds, and disulfide (sulfur) bonds. Among these, disulfide bonds are the most durable, ensuring hair flexibility and resistance to mechanical stress. Sulfur plays a direct role in maintaining these bonds, preventing hair breakage, split ends, and thinning [17].
🧅 Protection Against Oxidative Stress
Oxidative stress weakens hair follicles, leading to thinning and premature aging. Sulfur compounds act as natural antioxidants, reducing free radical damage that contributes to hair loss and follicle shrinkage [17].
How Much Sulfur Do Onions Contain?
Onions are one of the richest natural sources of sulfur. Studies show that onion bulbs contain between 8.42 mg/g and 0.18 mg/g dry weight (DW) of sulfur-based compounds, including diallyl sulfides, thiosulfinates, and S-alk(en)yl cysteine sulfoxides (ACSOs) [10]. These organosulfur compounds are what give onions their pungent aroma, but they also contribute to hair follicle stimulation and scalp health.
✅ Quercetin
The Role of Quercetin in Promoting Hair Growth
Quercetin, a powerful flavonoid found in onions and other plant sources, plays a crucial role in improving hair health and combating hair loss through multiple mechanisms:
🧅 Reduce Scalp Inflammation and Immune Attacks
Inflammation is one of the biggest causes of hair loss, affecting both autoimmune-related conditions like alopecia areata (AA) and hormonal hair loss.
💡 Research shows that quercetin blocks inflammatory proteins such as:
✔ TNF-α (Tumor Necrosis Factor Alpha)
✔ IL-1 (Interleukin-1)
✔ IL-6 (Interleukin-6)
These proteins attack hair follicles, causing excessive shedding and follicle miniaturization. When researchers treated mice with quercetin, inflammation decreased, and new hair started growing in bald areas. This suggests that quercetin may help prevent immune-driven hair loss[14].
🧅 Restores the Hair Follicle’s Natural Defense
Your hair follicles have a built-in defense system called immune privilege that keeps them protected from the immune system. But in autoimmune conditions like alopecia areata, this defense weakens, and the immune system mistakenly attacks hair follicles.
💡 Research also shows that quercetin helps restore immune privilege by reducing levels of Heat Shock Protein 70 (HSP70), a molecule that signals the immune system to attack follicles. When quercetin was applied in the study, HSP70 levels dropped, and the immune response against follicles was significantly reduced. This allowed hair to stay in the growth phase longer and prevented further immune-driven hair loss[14].
🧅 Blocks DHT to Prevent Androgenic Hair Loss
Androgenic alopecia (AGA), also known as male and female pattern baldness, is caused by dihydrotestosterone (DHT), a hormone that shrinks hair follicles over time.
💡 According to a study conducted by Zhang et al. (2023), quercetin inhibits 5α-reductase, the enzyme responsible for converting testosterone into DHT. Lower DHT levels mean hair follicles remain active for longer, preventing thinning and hair miniaturization.
Also, when combined with zinc (Zn²⁺) and copper (Cu²⁺), quercetin’s DHT-blocking effects were even stronger, making it a promising natural alternative to finasteride.
🧅 Activates Hair Follicle Stem Cells
For new hair to grow, hair follicle stem cells must be activated. When these stem cells become inactive, follicles remain dormant, leading to thinning hair.
💡 Study shows that quercetin also stimulates hair follicle stem cells, promoting the regeneration of weakened or dormant follicles. This means quercetin can help revive “sleeping” follicles, potentially regrowing hair in areas affected by hair thinning.
This effect was also enhanced when combined with Zn²⁺ and Cu²⁺, supporting healthy follicular activation [15].
🧅 Prolongs the Anagen (Growth) Phase
Hair grows in a cycle with three main phases:
🟢 Anagen (growth phase) — Hair actively grows
🟡 Catagen (transitional phase) — Follicles shrink
🔴 Telogen (shedding phase) — Hair falls out
When inflammation and DHT levels are high, hair follicles enter the shedding phase too soon.
💡 Studies show that quercetin helps extend the anagen (growth) phase of the hair cycle, allowing hair to stay fuller for longer. Wikramanayake et al. (2012) found that quercetin protected hair follicles from shrinking too soon. Similarly, research by Zhang et al. (2023) showed that quercetin boosted important growth-related genes (MMP-2, PDGF, and c-Myc), which help keep hair actively growing. The study also found that quercetin lowered levels of TGF-β1, a gene that signals hair to enter the shedding phase. By slowing down this process, quercetin may help hair grow longer and stay stronger.
🧅 Combats Oxidative Stress to Prevent Hair Aging
Oxidative stress can cause premature hair thinning, graying, and follicle damage.
💡Zhang et al. (2023) found that quercetin is a strong antioxidant that protects hair follicles from oxidative damage.This helps prevent follicular aging and supports long-term hair density. Also, antioxidants in quercetin keep hair stronger and more resistant to environmental stressors.
How Much Quercetin Do Onions Contain?
According to Patil, Pike, and Yoo (1995), yellow onions are the richest source of quercetin, with the Sweet Savannah variety containing up to 286.40 mg/kg fresh weight. In contrast, white onions have only trace amounts, making them the least beneficial for hair growth applications. Red and pink onions provide moderate quercetin levels, offering a balance between potency and formulation flexibility.
Additionally, storage conditions impact quercetin stability. Onions stored at 24°C experience a temporary increase in quercetin levels before a decline, whereas controlled atmosphere (CA) storage maintains more stable levels over time [19]. This highlights the importance of proper extraction and storage methods to preserve quercetin’s efficacy in hair growth treatments.For topical hair growth applications, yellow onion extract is the most potent source of quercetin, offering the highest potential for improving hair health and combating hair loss.
✅ Minerals
1. Zinc
The Role of Zinc in Promoting Hair Growth
🧅 Boosts Cell Growth
Zinc supports DNA and RNA synthesis, fueling hair follicle cell division and strand growth.
🧅 Regulates Hair Cycle
It prevents follicle shrinkage and speeds up recovery, pushing hair from resting (telogen) to growth (anagen) phase.
🧅 Shields Against Damage
As an antioxidant, zinc protects follicles from oxidative stress, preventing premature hair aging and loss.
💡 Clinical studies show that low zinc levels are associated with increased hair loss. Research on alopecia areata patients found that after 12 weeks of zinc supplementation, hair regrowth improved in 66.7% of participants [5].
2. Iron
The Role of Iron in Promoting Hair Growth
🧅 Iron Supports Hair Follicle Activity
Hair follicles are among the most metabolically active structures in the body, requiring a steady supply of oxygen and nutrients. Iron is essential for oxygen transport, ensuring that hair follicles receive the nourishment they need to sustain growth.
💡 Researchers found that women with female pattern hair loss (FPHL) had significantly lower ferritin levels compared to healthy controls (49.27 µg/L vs. 77.89 µg/L, p < 0.001). Premenopausal women were particularly affected, with ferritin levels as low as 30.67 µg/L, indicating a strong link between low iron stores and hair thinning [5].
How Much Zinc & Iron Do Onions Contain?
Onions are often praised for their quercetin content, but they’re also a natural source of zinc and iron—two minerals essential for healthy, thriving hair. While there’s no specific study yet on how onion-derived zinc and iron impact hair growth, extensive research on these minerals from other sources shows their crucial role in hair follicle function, growth cycle regulation, and scalp health.
📌 Zinc Content in Onions (mg per 100 g) [9]
🔴 Red Onions – Highest zinc content (4.45 to 5.09 mg)
🟡 Yellow Onions – 3.98 to 4.08 mg
⚪ White Onions – 3.22 to 3.78 mg
📌 Iron Content in Onions (mg per 100 g)[9]
🔴 Gandiol (Yellow Onion) – Highest iron content (3.48 mg)
🟡 Dayo (Yellow Onion) – 3.06 mg
⚪ White Grano (White Onion) – 1.74 mg
If you’re looking for science-backed ways to support hair growth, red onions provide the most zinc, while Gandiol yellow onions are highest in iron. Both minerals play a key role in hair follicle regeneration, oxygen delivery, and overall scalp health. While dietary intake is the most effective way to maintain optimal levels, onion-based serums and scalp treatments could provide additional topical support.
As always, evidence-based beauty is key—so while we wait for more targeted studies on onion-derived minerals for hair health, we already know zinc and iron are must-haves for strong, resilient hair.
How to Use Onion Juice for Hair Growth
If you’re ready to give onion juice a try, the key to success is knowing how to properly extract, apply, and combine it with other nourishing ingredients. This section walks you through everything you need to know to maximize its benefits while minimizing irritation.
Step-by-Step Guide to Extract Onion Juice
Extracting fresh onion juice at home is simple and requires only a few basic tools. Here’s how to do it:
What You’ll Need:
- 1–2 large onions
- A blender, grater, or juicer
- Cheesecloth or a fine mesh strainer
- A small bowl
- A spray bottle or cotton pad (for application)
Method:
Peel and Chop
Remove the onion skin and chop the onion into small pieces.
Blend and Grate
Place the pieces in a blender and process until you get a smooth pulp. If using a grater, finely grate the onion into a bowl.
Strain the Juice
Using cheesecloth or a fine mesh strainer, squeeze out the juice into a bowl, discarding the pulp.
Store Properly
Onion juice is best used fresh, but it can be stored in the refrigerator for up to 3 days in an airtight container.
DIY Onion Juice Recipes
While plain onion juice is effective on its own, combining it with other natural ingredients can enhance its potency and make application more pleasant.
1. Basic Onion Juice Treatment (For Direct Scalp Application)
- Freshly extracted onion juice
- Massage gently into the scalp for 15–30 minutes
- Rinse with a mild shampoo
2. Onion-Infused Oil (For Deep Nourishment)
- ½ cup coconut oil or castor oil
- 2 tablespoons onion juice
- Heat the oil slightly and mix with the juice
- Massage into the scalp and leave for 1 hour before washing
3. Onion and Aloe Vera Soothing Mask (For Sensitive Scalps)
- 2 tablespoons onion juice
- 2 tablespoons aloe vera gel
- 1 teaspoon honey (optional)
- Mix well, apply to the scalp, and leave for 20 minutes before rinsing
Precautions Before Use
Onion juice is powerful, but it can be irritating for some individuals. Follow these precautions:
- Patch Test First: Apply a small amount to your inner arm. If irritation occurs within 24 hours, avoid use on the scalp.
- Dilute If Needed: If onion juice feels too strong, mix it with water or aloe vera gel.
- Avoid Open Wounds: Do not apply to broken or irritated skin, as it may cause a burning sensation.
- Rinse Well: Always wash your scalp thoroughly after use to prevent buildup.
By following these steps, you can integrate onion juice into your hair care routine safely and effectively, leveraging its natural compounds for stronger, healthier hair.
Final Thoughts
If you’ve been searching for a natural, science-backed way to regrow and strengthen your hair, onion extract might just be the game-changer you need. With its rich sulfur content, powerful antioxidants, and essential nutrients, this humble kitchen ingredient has proven itself as more than just a culinary staple—it’s a hair-revitalizing powerhouse.
While it may not replace medical treatments for more severe hair loss, onion extract offers a safe, affordable, and effective alternative for those looking to reduce thinning, fortify strands, and promote healthier, fuller hair. If you’re ready to give your scalp the nourishment it craves, why not let science (and onions) do the work?
References
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- Galavi, A., Hosseinzadeh, H., & Razavi, B. M. (2021). The effects of Allium cepa L. (onion) and its active constituents on metabolic syndrome: A review. Iranian journal of basic medical sciences, 24(1), 3–16. https://doi.org/10.22038/ijbms.2020.46956.10843
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- Kwak, J.-H., Seo, J. M., Kim, N.-H., Arasu, M. V., Kim, S., Yoon, M. K., & Kim, S.-J. (2017). Variation of quercetin glycoside derivatives in three onion (Allium cepa L.) varieties. Saudi Journal of Biological Sciences, 24(6), 1387–1391. https://pmc.ncbi.nlm.nih.gov/articles/PMC5562462/pdf/main.pdf
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By using this website, you agree that The Chemist Beauty Insider assumes no liability for any decisions made based on its content. Perform a patch test before applying any new ingredient, and discontinue use if irritation occurs.
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Ready to Revive Your Hair Naturally?
If you’re looking for a science-backed, natural way to support hair growth, strengthen your strands, and nourish your scalp, onion extract could be the missing piece in your hair care routine.
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