Propylene glycol: what does it mean for your scalp and hair?

Many people who use minoxidil for hair loss encounter the ingredient propylene glycol. Sometimes it is also written as 'propylene glycol'.

But what exactly does propylene glycol do? And can it affect your scalp or even your hair growth?

In this article, we explain what you need to know.

What is propylene glycol?

Propylene glycol (PG) is a commonly used excipient or solvent for medicines. It is added because it:

• makes active ingredients more soluble (in the base, such as a solution)
• can improve the absorption of ingredients by the skin
• helps to stabilize a medicine in a solution (this ensures that it has a longer shelf life and continues to work well)

Propylene glycol is used in minoxidil 5% solution , a medicine used for hereditary hair loss (androgenetic alopecia).

According to safety assessments of ingredients and excipients, the solvent propylene glycol is in most cases considered safe for normal use ⁶ .

Propylene glycol and the skin: possible irritation

Although propylene glycol is safe for most people, it can cause skin irritation in a small proportion of users. Dermatological research shows that symptoms can be ^1,2 :

• redness of the skin
• itch
• burning sensation
• scaling

In rare cases, a contact allergy to propylene glycol can develop ^3,4,5 . This means that the skin reacts specifically to PG (propylene glycol). This does not occur often, but dermatologists do see it regularly in people who use products with high concentrations of PG.

Side effect of minoxidil: is that due to propylene glycol?

When people experience symptoms with minoxidil solution , such as itching or flaking on the scalp, this is usually not due to minoxidil itself. Also read our article about side effects of minoxidil on the scalp .

In many cases, propylene glycol turns out to be the cause of the irritation ⁹ .

This is because PG:

• can affect the skin barrier
• can make the skin more sensitive
• can trigger an irritation reaction in some people

Research suggests that propylene glycol can interact with lipids in the skin barrier, potentially making the skin more sensitive ^7. Lipids form a protective layer that is important for healthy, hydrated skin.

Why a healthy scalp is important

The scalp is a unique environment with:

• hair follicles
• sebaceous glands
• own microorganisms of bacteria and yeasts – essential for a healthy and protected scalp

When irritation occurs, this can lead to inflammation, scaling, dandruff, itching, or redness.

When the scalp is inflamed or infected, for example due to eczema (seborrheic eczema) or dandruff, this can lead to hair loss. This happens because the inflammation and the disturbed balance of the scalp can damage the hair roots ^11,12 . The good news is that this hair loss is usually temporary. When the inflammation is treated properly with, for example, antifungal shampoo or other medication, the hair can grow back.

A healthy scalp therefore helps keep the skin in balance and is the best foundation for healthy hair growth.

Important to know

There is no evidence that propylene glycol directly causes hair loss. It may lead to side effects on the scalp in some people. This can feel unpleasant and, if it leads to infection or inflammation, be adverse for hair growth ^11,12 .

PG-free minoxidil foam: an alternative

To reduce skin irritation, there are now also minoxidil products without propylene glycol.

A well-known example is minoxidil 5% foam without propylene glycol .

In clinical studies, this formulation was often better tolerated by the scalp than the classic solution with PG ⁸ .

For people with sensitive skin, this can be a good alternative.

Important to remember

A healthy scalp is the best foundation for healthy hair follicles and hair growth.

Minoxidil 5% solution contains propylene glycol (PG), an ingredient that may cause irritation in a small proportion of users, such as redness, itching, or scaling.

 

This may be a reason to choose PG-free minoxidil 5% foam . Note: this product can also cause similar local side effects ¹³ .

Other ways to keep your scalp calm and healthy are:

• use a skin-friendly shampoo
• Don't wash your hair too often
• avoid aggressive bleach or dyes
• protect your scalp from the sun

FAQ – Frequently Asked Questions

Is propylene glycol harmful?

According to safety assessments of cosmetic ingredients, propylene glycol is considered safe for normal use ^6. However, a small proportion of people may experience skin irritation.

What are the side effects of minoxidil on the scalp?

Possible side effects may include:

• itch
• redness
• scaling
• a burning sensation

These complaints are often caused by propylene glycol in the solution, and not by minoxidil itself ^9,14 .

Can propylene glycol cause hair loss?

There is no scientific evidence that propylene glycol directly causes hair loss.

However, scalp irritation can be cosmetically bothersome. Indirectly, propylene glycol can contribute to the development of inflammation or infection. In that case, it can lead to temporary hair loss ^11,12 .

Why does minoxidil foam cause less irritation?

Minoxidil foam contains no propylene glycol. As a result, the risk of scalp irritation is reduced. Clinical research shows that users of the foam experience local side effects less frequently ⁸ .

What should I do if I experience itching, redness, or scaling while using minoxidil?

If you experience symptoms:

• temporarily stop using the product
• consult a doctor or pharmacist
• If you use solution, consider minoxidil foam without propylene glycol.

References

1. Zug, KA, et al. (2009). Patch test results of the North American Contact Dermatitis Group 1996–2006. Dermatitis, 20(3), 149–160.
2. Warshaw, E.M., et al. (2018). Contact dermatitis associated with propylene glycol. Dermatitis, 29(4), 204–210.
3. Pemberton, R., & Wilkinson, M. (2023). Contact allergy to propylene glycol. Contact Dermatitis, 89(4), 247–256.
4. Lessmann, H., et al. (2005). Contact allergy to propylene glycol. Contact Dermatitis, 53(5), 247–256.
5. Patel, VM, et al. (2023). Clinical relevance of positive patch test reactions to propylene glycol. Dermatitis, 34(3), 195–201.
6. Cosmetic Ingredient Review Expert Panel. (2012). Safety assessment of propylene glycol. International Journal of Toxicology, 31(5 Suppl), 245S–260S.
7. Zhang, Y., et al. (2024). Molecular dynamics simulation of propylene glycol interaction with stratum corneum lipids. Journal of Molecular Modeling, 30(2), 52.
8. Blume-Peytavi, U., et al. (2011). Randomized controlled trial of 5% minoxidil foam. Journal of the American Academy of Dermatology, 65(6), 1126–1134.
9. Friedman, E. S., et al. (2002). Allergic contact dermatitis to topical minoxidil solution. Dermatitis, 13(4), 201–205.
10. Sarkar, R., et al. (2020). Study comparing propylene glycol–based solution vs alternative minoxidil formulation. International Journal of Trichology, 12(5), 197–203.
11. Shah RR, Larrondo J, Dawson T, McMichael A. Scalp microbiome: A guide to better understanding scalp diseases and treatments. Archives of Dermatological Research. 2024.
12. Limbu SL, Purba TS, Harries M, et al. Dandruff lesional scalp skin exhibits epidermal T cell infiltration and a weakened hair follicle immune privilege. International Journal of Cosmetic Science. 2024.
13. SMPC minoxidil 5% foam (Linn Pharma) https://www.geneemiddelinformatiebank.nl/bijsluiters/h128704.pdf
14. SMPC minoxidil 5% solution (Linn Pharma) https://www.geneemiddelinformatiebank.nl/bijsluiters/h122548.pdf