Phil Richardson a Commercial Consultant to the dermatology industry sheds light on the organic compound menthol, and its role as itch relief
Menthol is used in a vast array of over-the-counter medications, despite this, the understanding of the clinical pharmacology of menthol remains incomplete. However, considering the extensive use of menthol there have been only a few reports of adverse dermatological effects.
Menthol is an organic compound made synthetically or obtained from peppermint or other mint oils.
Menthol is primarily used for its cooling effect when applied to the skin. This effect is observed at low concentrations and it is due to a specific action of menthol on sensory nerve endings and is similar to capsaicin, the chemical responsible for the spiciness of hot chillies (which stimulates heat sensors, also without causing an actual change in temperature).
In concentrations of 1% or less, menthol depresses cutaneous sensory receptors, while at concentrations between 1.25% and 16%, it stimulates sensory receptors and thus acts as a counter-irritant. This is potentially why menthol is frequently found in a variety of topical pain relief medications because of its counter-irritant and local anaesthetic properties.
Many consultant dermatologist & GP’s frequently prescribe menthol, in a range of different strengths, usually in a cream base, for non-specific pruritus, commonly found in elderly patients.
There are many causes of itching. Liver disease can cause itching, and even itching associated with pregnancy – obstetric cholestasis. Obstetric cholestasis is a liver disorder that occurs in around one in 140 pregnancies in the UK. Also referred to as intrahepatic cholestasis of pregnancy, it is a condition in which the normal flow of bile out of the liver is reduced. Chemicals in the bile called bile salts build-up and ‘leak’ into the bloodstream. A characteristic of this condition is itching or pruritus, which generally appears in the last 3 months of pregnancy but can appear sooner. It is of variable severity and can be extremely distressing for the mother. Both the raised bile salts and pruritus completely disappear soon after birth and do not appear to cause long-term health problems for mothers.
Itching is often the only symptom of obstetric cholestasis. The itching typically begins on the arms, legs, hands and soles of the feet. It may also occur on other parts of the body such as the face, back and breasts. It is usually worse at night, leading to sleeplessness and exhaustion.
It is important that women who are pregnant and itching should check with their doctor or midwife.
As with all itching, it is important to exclude all other possible causes. Doctors will often prescribe menthol in an Aqueous cream base to help with itching caused by liver disease, including usually temporary conditions such as obstetric cholestasis.
Menthol. Wikimedia (cited 2014 May 30) Available from URL: http://en.wikipedia.org/wiki/Menthol
Tejesh Patel, Yozo Ishiuji &Gil Yosipvitch, Menthol a refreshing look at this ancient compound J Am Acad Dermatol, November 2007 British Liver Trust – Pioneering Liver Health 2014 May 30 Available from URL: http:// www.britishlivertrust.org.uk/
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