INGREDIENT · EMOLLIENT
Propylene glycol in skincare: irritation, allergy and facts
Propylene glycol has a worse reputation than its record deserves, and a better one than its detractors would like. It is a weak allergen that gets tested on a lot of patients.
You may see it written as
- Propylene Glycol
What propylene glycol is
Propylene glycol is an emollient and emulsifier found in cosmetics, medications and food. In 2018 it was named Allergen of the Year by the American Contact Dermatitis Society, a title that sounds worse than it is. A systematic review calls it both a weak sensitiser and an irritant, which confuses patch test results.1
It is also used as a co-solvent and to help drugs get through the skin. In lab work, it acted as a penetration enhancer for every compound tested, particularly water-loving ones.2 That matters if you use it with an active. One of its authors works for a pharmaceutical company.2
How often it actually causes a reaction
The biggest data set we found tested 45,138 patients with 20% propylene glycol in water over ten years. 2.3% tested positive, 2.4% had a doubtful or follicular reaction, and 0.6% had a clear irritant reaction. The authors read that profile as a slightly irritant preparation, meaning many of the weak positives are probably false. They found no everyday exposure that raised risk, except lower-leg dermatitis, and concluded that the risk of sensitisation on healthy skin looks very low.3
So the picture is not that propylene glycol is dangerous. It is that it is common enough that, in a large group of people referred for patch testing, some people show reactions. The one group where risk looked higher was people with lower-leg dermatitis.3
Using propylene glycol with other actives
Because it can help other ingredients through the skin, propylene glycol may change how an active behaves. The lab studies tested drugs, though, not cosmetic actives, so we cannot say what it does to the strength of a vitamin C serum or a retinoid. We did not find a study that answers that.
Propylene 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
The names to look for are Propylene Glycol. In Snifff, it reads as Low risk. For the rest of the formula, see what the score means and how to read the list.
As Snifff shows itPropylene 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 propylene glycol
Is propylene glycol bad for skin?
For most people on healthy skin, no. A patch-test study of 45,138 patients concluded the sensitisation risk on healthy skin is very low,3 although it is a weak irritant and allergen.1
Can propylene glycol cause an allergy?
It can, rarely. In that study, 2.3% of patients tested positive to 20% propylene glycol, and the authors thought many of those weak reactions were false positives.3
Does propylene glycol help other ingredients absorb?
In laboratory tests, it enhanced the skin penetration of all the compounds studied, especially water-loving ones.2
Is propylene glycol safe in pregnancy?
Snifff found no pregnancy-specific evidence for Propylene glycol. Ask your doctor or midwife about the product you use.
WHERE THIS COMES FROM
Sources
- Propylene glycol in contact dermatitis: a systematic reviewMcGowan MA, et al. · Dermatitis · 2018
- Effect of propylene glycol on the skin penetration of drugsCarrer V, et al. · Archives of Dermatological Research · 2020
- Skin-sensitizing and irritant properties of propylene glycolLessmann H, et al. · Contact Dermatitis · 2005
- 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.