What Is Menthol, Is It Harmful? How Does the Cooling Sensation Arise?

The coolness you feel in a shampoo, a shaving product or a pain cream is not a temperature change but a nerve message. Menthol, which occurs naturally in mint species and is also produced synthetically, appears on labels as Menthol and is added for scent and freshness. It binds to TRPM8, a receptor on cold-sensing nerve endings in the skin. This receptor normally opens in the cold, and menthol opens it in the same way. The brain reads the message as "cold", while the skin may not actually have cooled at that moment.

Why does feeling cold not mean cooling?

This difference has been measured. In 12 people walking in the heat, when a 4% menthol gel was applied, they felt cooler, but the rise in core body temperature was greater (0,7 and 0,4 °C) and sweating decreased. The body appears to read "I've cooled" and reduce its cooling response. In another study, 4% menthol markedly increased skin blood flow. So the skin can work in the opposite direction to the sensation.

The last row matters. A menthol shampoo refreshes the scalp, but that does not show that dandruff has decreased or that the scalp is healthy.

What else does it do to the skin?

In a small human study (18 people), menthol did not reduce itching induced by histamine and did not change pain thresholds. Water loss from the skin increased in the area where menthol was applied; the researchers read this as a sign of an irritant effect. At very high concentrations the reverse happens: 40% menthol is used in pain research as a model, because it causes cold pain and increased sensitivity to pain. Do not read a burning sensation as "it's working".

Is menthol harmful, and who should be careful?

Short answer: in low-concentration rinse-off products most people have no problems, but it is not suitable for every skin.

• Sensitive skin and rosacea: If you redden often, do not make products containing menthol, mint and camphor your first choice. You can find triggers on the rosacea page.
• Babies and small children: Do not apply products containing mint oil and menthol to the face or around the nose; respiratory problems have been reported. The essential oils article discusses this group separately.
• Pain creams: In the US, 43 chemical burn cases linked to non-prescription pain creams were compiled in 2012, and most second- and third-degree burns were related either to products containing only menthol or to those combining more than 3% menthol with more than 10% methyl salicylate. A rare situation, but do not apply to damaged skin, and do not cover with a tight bandage or heat.
• Allergy: In the EU, with the 2023 regulation, menthol was added to the list of fragrance allergens that must be named separately. The limit is 0,001% in leave-on products and 0,01% in rinse-off products. This is not a ban; it is so that people with allergies can see it. Try a new product on the inner arm or elbow crease, twice a day, for 7-10 days.

If the burning sensation does not pass within a few minutes, wash off the product and do not use it. If blisters or burns appear where you applied it, or breathing difficulty begins, see a doctor.