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Butylene Glycol

Also known as: 1,3-Butylene glycol, 1,3-Butanediol

A cosmetic solvent and humectant whose formulation role is better established than any standalone skin-treatment claim.

Unlabelled clear glass vial and a transparent droplet on a linen surface
Editorial illustration

Cosmetic butylene glycol usually refers to 1,3-butanediol, a solvent and humectant. The published CIR assessment supported the cosmetic uses it evaluated, but contact allergy has subsequently been reported. Its presence on a label describes a formulation ingredient, not a proven anti-aging or disease-treatment active.1, 2, 3

  • 1,3-Butanediol is the compound identified by PubChem CID 7896.1
  • The 1985 CIR group report describes humectant and solvent roles.2
  • A contact-allergy case report cannot establish the rate of allergy in all users.3

What is Butylene Glycol?

This guide concerns 1,3-butylene glycol, CAS 107-88-0. It is not the same molecule as propylene glycol, hexylene glycol or ethylene glycol. The shared word glycol is not enough to transfer a chemical's hazard or a clinical result to another compound.1, 2

Where it comes from

Natural sources

  • A defined diol rather than a botanical extract; the ingredient name does not establish a plant source

How it's made

Commercial material is manufactured and purified; supplier records identify the production route.

What it does in products

  • Solvent in cosmetic formulations
  • Humectant and formulation aid

Benefits

Humectancy and formulation performance

limited evidence

Butylene glycol helps serve the formula's moisture and solvent functions. Those functions are not evidence of a standalone wrinkle or skin-disease treatment.2

The foundational CIR report combines toxicology and human patch-test data. It is a safety assessment, not a comparative trial of long-term consumer skin improvement.

Evidence scope and limitations

Topical cosmetic 1,3-butylene glycol; not other butanediol isomers, ingestion or medical-use dosing.

  • PubChem supports identity only, not a clinical benefit.
  • The foundational safety assessment is old and is not a finished-product efficacy trial.
  • A case report identifies possible allergy but supplies no population risk estimate.

Evidence last checked: 2026-10-09

Side effects & safety

Irritation or allergic contact dermatitis (varies)The earlier patch tests did not exclude individual allergy. A published 2020 case report identifies that possibility without estimating population incidence.

Safety considerations

  • No universal compatibility claim for prescription-skincare combinations follows from these sources.
  • Not for: Avoid butylene glycol if it is an established personal contact allergen.
  • Not for: Persistent dermatitis warrants professional assessment of the whole product; avoid eye exposure and follow label directions.
2, 3, 4

Amounts studied & product use

These figures describe research or common product use, not a personal dose or treatment recommendation.

In skincare studies and products

No optimal consumer concentration or DIY dose is established here. CIR's assessment concerns the cosmetic uses described in its report; raw-material patch testing is not an instruction to apply undiluted glycol.

2

Regulatory status

  • Cosmetics are generally not FDA-preapproved. A cosmetic ingredient listing does not authorize medical-treatment claims.
  • INCI name on cosmetic labels: Butylene Glycol.
  • The published 1985 final group assessment concluded safety for the cosmetic uses then evaluated. That historical conclusion is not a guarantee against individual allergy.
2, 5

A negative patch test is not a lifetime allergy guarantee

CIR's earlier testing and a later contact-allergy report answer different questions: tolerability in tested participants versus a reaction in an individual. The case report does not invalidate every use, and the earlier study cannot erase the case.

Our reading: a history of dermatitis is a reason to investigate the actual formulation and allergen, not to label all glycols harmful or to dismiss a reaction because an ingredient has a safety assessment.

2, 3, 4

Frequently asked questions

Is butylene glycol the same as propylene glycol?

No. This entry covers 1,3-butanediol. Related glycol names describe different compounds and should not be used as substitutes in a safety conclusion.1, 2

Can it cause allergy despite the CIR conclusion?

Yes, an individual case has been reported. That does not establish how frequently allergy occurs; a clinician can investigate suspected contact dermatitis.3, 4

The bottom line

Read butylene glycol as a formula component. Compound identity, exposure and personal allergy history are more useful than a blanket glycol rule.

References

  1. 1,3-Butanediol: compound record. NCBI PubChem · ingredient monograph · CID 7896; CAS 107-88-0; identity only; accessed October 9, 2026
  2. Final Report on the Safety Assessment of Butylene Glycol, Hexylene Glycol, Ethoxydiglycol, and Dipropylene Glycol. Journal of the American College of Toxicology (1985) · safety assessment · DOI 10.3109/10915818509078692; volume 4, issue 5
  3. Blomberg M, Johansen JD. Allergic contact dermatitis due to butylene glycol in cosmetics. Contact Dermatitis (2020) · primary study · PMID 32342510; DOI 10.1111/cod.13581; case report
  4. Allergens in Cosmetics. U.S. Food and Drug Administration · government guidance · Undated resource; accessed October 9, 2026
  5. FDA Authority Over Cosmetics: How Cosmetics Are Not FDA-Approved, but Are FDA-Regulated. U.S. Food and Drug Administration (2013) · government guidance

Revision history

  1. Initial AI-assisted source checks and claim-level citation mapping under the site-authorized publishing workflow. No separate human or independent medical review is claimed.