Peppermint oil: potential risks to be aware of?

The key takeaway.

Peppermint essential oil must always be diluted (≈ 5%) to prevent irritation.
Isolated cases of contact dermatitis have been reported following the use of peppermint essential oil.
The high content of menthol, menthone, and isomenthone in peppermint essential oil confers a neurotoxic potential in the event of overdose, justifying its contraindication during pregnancy, breastfeeding, and in children under 6 years of age.
Certain medical conditions (atrial fibrillation, G6PD deficiency, asthma, epilepsy, liver disorders) require a prior medical advice before using peppermint essential oil.
As with any active ingredient, we recommend testing peppermint essential oil on a small area of skin before adding it to your skincare routine.

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What is peppermint essential oil?

The peppermint essential oil is obtained from Mentha × piperita, a hybrid plant resulting from the cross between water mint (Mentha aquatica) and spearmint (Mentha spicata). It is generally extracted from the aerial parts of the plant, mainly the leaves, by steam distillation. This process allows for the concentration of volatile aromatic compounds, giving rise to an essential oil very rich in active molecules, including menthol and menthone. Known since ancient times, the peppermint was already used for its digestive, stimulating, and refreshing properties, as well as for its intense and recognizable fragrance.

Today, peppermint essential oil is used in many fields. In aromatherapy, it is valued for its invigorating and cooling effects. In cosmetics, it is incorporated into purifying treatments aimed at alleviating heavy-leg sensations or even in hair care products. Peppermint essential oil is also found in certain hygiene, food, or household products.

What are the potential risks associated with peppermint essential oil?

When administered at the correct dosage, peppermint essential oil is generally considered safe.

However, like all essential oils, it remains a highly concentrated blend of active compounds, which explains why adverse effects linked to peppermint essential oil may occur, particularly in people with sensitive skin. Moreover, its main compound, menthol, tends to stimulate the skin’s cold receptors, which can lead to intense cooling sensations as well as tingling, burning, or irritation when it is applied undiluted or insufficiently diluted.

Peppermint essential oil also contains allergens, which are found in many essential oils—such as limonene or linalool—that can trigger reactions of the type contact dermatitis. A review combining studies on over 28,000 patients tested by patch test with 2% peppermint essential oil in petrolatum showed that 0.6% of them exhibited an allergic reaction, primarily in the form of irritation. Although this percentage remains relatively low, it confirms the existence of side effects from peppermint essential oil, particularly in sensitive skin.

Moreover, peppermint essential oilis not considered a sensitizer in the toxicological sense. As a reminder, a sensitizing substance can induce an allergic reaction after repeated exposures, even at low doses. This conclusion is based on the results of a Kligman test, a standardized protocol. Nevertheless, as with many essential oils, isolated cases of skin sensitization have been reported, which underscores the importance of exercising caution.

Peppermint essential oil: what are the contraindications and precautions for use?

5.4%

Maximum concentration of peppermint essential oil not to be exceeded, as specified in Essential Oil Safety: A Guide for Health Care Professionals.

This limit is explained in part by the presence of pulegone and menthofuran in peppermint essential oil, potentially toxic compounds at high doses. Because of these risks, the authors further recommend completely avoiding its use in certain populations, particularly in people with atrial fibrillation or a glucose-6-phosphate dehydrogenase (G6PD) deficiency.

To minimize the risk of a skin reaction, we also recommend that you perform a patch test before using any skincare product containing peppermint essential oil. This involves applying a small amount of the product to the inner crease of the elbow and waiting 24 hours. The absence of redness, itching, or a burning sensation is a reliable indicator of skin tolerance.

It should also be noted that peppermint essential oil exhibits neurotoxic potential, mainly due to its high content of menthol, menthone, and isomenthone—molecules belonging to the ketone family. These compounds have the ability to cross the blood-brain barrier and, in the event of an overdose or prolonged use, could impair nervous system function by altering the myelin sheath that protects neurons.

For these reasons, peppermint essential oil is contraindicated during pregnancy, and is not recommended for breastfeeding women or children under 6 years of age.

Finally, although the peppermint essential oil can be administered orally, it is advisable that this practice be undertaken under medical advice, for a short period and at limited doses (generally no more than 3 drops per day). Furthermore, individuals with asthma, diabetes, epilepsy, liver disorders, or hormone-dependent cancers should consult a healthcare professional before any use, as this essential oil may interact with certain medications and alter their effectiveness.