According to CosIng, ALLIUM CEPA BULB OIL is the volatile oil obtained from onion bulbs. Hair products sold as onion oil are most often macerates or blends, whose INCI differs.

Onion oil

Q: What are the benefits of onion oil in cosmetics?

CosIng gives it only an antimicrobial function. We found no peer-reviewed study measuring a cosmetic effect of an onion oil: this page announces none.

Q: Is onion oil good for hair?

The published studies cover onion juice or extract, not an oil. The reviews judge the evidence limited (small samples, short durations, conflicts of interest). This page claims no hair benefit.

Q: Does onion oil stop hair loss?

We do not claim it, and a cosmetic product cannot claim this effect. The published trial covers raw juice and a medical endpoint.

Q: Can onion oil irritate the skin?

Onion allergy is described among the possible causes of contact skin reactions, and an onion extract gel caused more adverse effects than the comparators in a meta-analysis. Every formula must be tested on the finished product.

Q: Is onion oil regulated in cosmetics?

No specific restriction applies in the EU. It is not on the list of fragrance allergens to declare. The general safety obligations for the finished product still apply.

Q: Can you manufacture an onion oil product for my brand?

No formula in our catalog features it. Our formulation lab can study a custom formula, after checking the raw material and running tolerance tests. ISO 22716 certified lab, free samples.

CosIng describes Allium cepa bulb oil as the volatile oil of onion bulbs, with an antimicrobial function1. Hair products sold as onion oil do not contain the same ingredients. The published trials cover onion juice or extract, not an oil2 3, and the reviews judge the evidence limited5 6. We claim no benefit.

Mohamed El HjoujiFounder and CEO · Updated November 3, 2026 · Reading time 5 min

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Onion oil at a glance

Entry from our cosmetic ingredient glossary. Regulatory data from the European Commission's CosIng database1. Copy the INCI in one click for your files.

INCI name: ALLIUM CEPA BULB OILCosIng: volatile oil obtained from the bulbs of Allium cepa1
Other names: Onion oilOnion oil. The term also covers onion macerates in another oil, whose formula INCI differs: rely on the specification sheet
CAS number: None in CosIngThe CosIng entry gives none; we do not list one1
EC number: None in CosIngSame reason1
Botanical origin: Onion (Liliaceae)Volatile oil from the bulbs of Allium cepa1
CosIng function: Antimicrobial"Antimicrobial": this is the only function listed1
EU status: No restriction specific to the ingredientNot listed in Annexes II to VI of Regulation (EC) 1223/2009, consolidated May 1, 20251 7
Allergen to declare: Not as a fragrance allergenNot listed in Annex III or in the fragrance allergen list of Regulation (EU) 2023/1545; onion can nevertheless sensitize7 4
Safety (CIR, SCCS): No assessment retainedWe retained no CIR or SCCS assessment for this oil

What the research says

Each result shows the protocol and the level of evidence. The higher the level, the better the result carries over to a finished formula.

Clinical trialReview or consensusLaboratory

Hair and scalpHaircare

Studies on onion juice, not on the oil

Review

2025 reviews

The reviews list onion juice among the herbal remedies for hair loss, with small samples, short durations and conflicts of interest, and call for better designed trials5 6. The products studied are most often combined formulations6.

A medical trial, outside the cosmetic field

Clinical trial

Controlled trial38 peopleRaw onion juice versus tap water, 2 months

This trial covers raw juice, not an oil, and a medical type of hair loss. We do not use its results as a cosmetic claim2.

Skin and toleranceSkin tolerance

An onion extract gel that is less well tolerated

Review

2021 meta-analysis13 randomized trialsSkin after surgery

The onion extract gel increased the incidence of adverse effects compared with no product (P < 0.0001) and with other products (P = 0.008), and discontinuations due to intolerance (P = 0.0002). Only tolerance is reported here: this is an extract in a gel, not an oil3.

Allium allergy: a rising frequency

Review

2014 reviewOnion and garlic

Garlic and onion allergy is one of the possible causes of contact skin reactions. The authors link the rise in production and use to more frequent problems4.

This page summarizes published literature on a cosmetic ingredient. For onion oil, no study covers the oil itself: we say so rather than carry over results obtained with juice or an extract. It does not describe the effect of a finished product and it is not medical advice.

Which products can use onion oil?

No formula in our white label catalog features onion oil yet. Our formulation lab can add it to a custom formula or to a catalog formula. Its common uses:

Hair

Hair oils and scalp oil baths, as a supporting ingredient at a low dose.

Frequently asked questions about onion oil

What is onion oil?

According to CosIng, ALLIUM CEPA BULB OIL is the volatile oil obtained from onion bulbs1. Hair products sold as onion oil are most often macerates or blends, whose INCI differs.

What are the benefits of onion oil in cosmetics?

CosIng gives it only an antimicrobial function1. We found no peer-reviewed study measuring a cosmetic effect of an onion oil: this page announces none.

Is onion oil good for hair?

The published studies cover onion juice or extract, not an oil. The reviews judge the evidence limited (small samples, short durations, conflicts of interest)5 6. This page claims no hair benefit.

Does onion oil stop hair loss?

We do not claim it, and a cosmetic product cannot claim this effect. The published trial covers raw juice and a medical endpoint2.

Can onion oil irritate the skin?

Onion allergy is described among the possible causes of contact skin reactions4, and an onion extract gel caused more adverse effects than the comparators in a meta-analysis3. Every formula must be tested on the finished product.

Is onion oil regulated in cosmetics?

No specific restriction applies in the EU1 7. It is not on the list of fragrance allergens to declare7. The general safety obligations for the finished product still apply.

Can you manufacture an onion oil product for my brand?

No formula in our catalog features it. Our formulation lab can study a custom formula, after checking the raw material and running tolerance tests. ISO 22716 certified lab, free samples.

Sources

Peer-reviewed studies and official regulatory sources, checked on November 3, 2026.

European Commission. CosIng, entry ALLIUM CEPA BULB OIL (no CAS or EC number listed). CosIng 104190
Sharquie KE, Al-Obaidi HK. Onion juice (Allium cepa L.), a new topical treatment for alopecia areata. J Dermatol. 2002;29(6):343-346. doi:10.1111/j.1346-8138.2002.tb00277.x
Yuan X, Shen J, Chen L, et al. Onion extract gel is not better than other topical treatments in scar management: a meta-analysis from randomised controlled trials. Int Wound J. 2021;18(3):396-409. doi:10.1111/iwj.13542
Cantisani C, Visconti B, Paolino G, et al. Unusual food allergy: Alioidea allergic reactions overview. Recent Pat Inflamm Allergy Drug Discov. 2014;8(3):178-184. doi:10.2174/1872213x08666141107170159
Ahmed A, Alali AM, Abdullah E, et al. Herbal remedies for hair loss: a review of efficacy and safety. Skin Appendage Disord. 2025;11(4):360-371. doi:10.1159/000542876
Bikash C. Topical alternatives for hair loss: beyond the conventional. Int J Trichology. 2025;17(1):13-19. doi:10.4103/ijt.ijt_8_23
European Parliament and Council. Regulation (EC) No 1223/2009 on cosmetic products, consolidated version of May 1, 2025 (Annexes II to VI, Article 17). EUR-Lex. EUR-Lex 1223/2009

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Onion oil at a glance

What the research says

Hair and scalpHaircare

Studies on onion juice, not on the oil

A medical trial, outside the cosmetic field

Skin and toleranceSkin tolerance

An onion extract gel that is less well tolerated

Allium allergy: a rising frequency

Which products can use onion oil?

Hair

Frequently asked questions about onion oil

Further reading

Sources

Tell us about your project