INGREDIENT · GLYCOL
Butylene glycol in skincare: a common solvent, explained
Butylene glycol is a workhorse ingredient in serums and creams. Its main safety review is from 1985, and newer patch-test data add some detail.
You may see it written as
- Butylene Glycol
What butylene glycol is
A 1985 safety review groups butylene glycol with hexylene glycol, ethoxydiglycol and dipropylene glycol. It describes them as viscous liquids used in cosmetics as humectants, emulsifiers, plasticisers and solvents.1
What the safety review found
Animal studies pointed to a low order of toxicity. Butylene glycol caused minimal to mild irritation of rabbit skin. Undiluted, it was not an eye irritant in rabbits but was in humans.1
In human patch tests, undiluted butylene glycol produced a very low order of primary skin irritation, and a repeated insult patch test produced no evidence of skin sensitisation. The panel concluded the glycols in the report are safe as presently used in cosmetics.1
What newer allergy data says
A 2026 study from a Belgian hospital analysed 1,979 patients patch tested with at least one glycol between 2021 and 2024. It found 2.79% were allergic to propylene glycol, 6.74% (6 of 89) to pentylene glycol and 0.77% or 0.12% to caprylyl glycol, depending on the test concentration. Cosmetics were the most common exposure source. Cross-reactivity seemed limited and most evident among structurally similar short-chain glycols.2
The abstract does not report results for butylene glycol. It shows that glycols as a group can cause contact allergy in some people, and does not say how often butylene glycol does.
How to read this
Butylene glycol has a reassuring older safety review. Newer patch-test data show allergy to it is uncommon but does occur: in a 2024 US clinic study, 13 of 893 patients tested (1.46%) reacted to it, and 6 of those 13 also reacted to propylene glycol.3 People with a known glycol allergy may want to check labels.
Using butylene glycol with other products
We did not find a source on combining butylene glycol with other products.
Butylene glycol in pregnancy and breastfeeding
We found no pregnancy- or lactation-specific evidence for this ingredient.
Evidence on cosmetic products in pregnancy is limited overall, so ask your doctor or midwife about the specific product you use.4
What you will see on the label
On a label, look for Butylene Glycol. Snifff shows it as Risk-free. For the rest of the formula, see what the score means and how to read the list.
As Snifff shows itButylene Glycol
Pregnancy and nursing
We found no pregnancy- or lactation-specific evidence for this ingredient.
Wording as it appears in the extension, which can change between releases.
A FEW MORE ANSWERS
Common questions about butylene glycol
What is butylene glycol?
A viscous liquid used in cosmetics as a humectant, emulsifier, plasticiser and solvent.1
Is butylene glycol safe?
A 1985 safety review found very low irritation in human patch tests and no sensitisation in a repeated insult patch test, and concluded it is safe as presently used in cosmetics.1 A 2024 US study found 1.46% of 893 patch-tested patients reacted to it.3
Can butylene glycol cause allergy?
A 2026 study found contact allergy to propylene glycol, pentylene glycol and caprylyl glycol in patch-tested patients. Its abstract does not report butylene glycol.2
Is butylene glycol safe in pregnancy?
Snifff found no pregnancy-specific evidence for Butylene glycol. Ask your doctor or midwife about the product you use.
WHERE THIS COMES FROM
Sources
- Final Report on the Safety Assessment of Butylene Glycol, Hexylene Glycol, Ethoxydiglycol, and Dipropylene GlycolCosmetic Ingredient Review Expert Panel · Journal of the American College of Toxicology · 1985
- Contact allergy and allergic contact dermatitis from propylene glycol and related glycols: cosmetic skin sensitisers after all?Kanokrungsee S, Dendooven E, Aerts O · Contact Dermatitis · 2026
- Cross-reactivity between propylene glycol and butylene glycolEkstein SF, Battis N, Dabrowski D, Neeley AB · Dermatitis · 2024
- Cosmetic dermatology in pregnancy and lactation: a risk-benefit framework for clinical practiceKovacs T, et al. · International Journal of Dermatology · 2026
This page explains an ingredient. It is not medical advice, and it is not an assessment of any product. If you are pregnant, breastfeeding, or have a skin condition, ask your doctor or pharmacist.