When a generalised itch is more than skin-deep

MEDICAL MATTERS:Itching can signal an underlying problem, but usually it is not a sign of serious disease, writes Muiris Houston

"Tis better than riches to scratch when it itches"

- Anon.

Itch must be one of the most annoying symptoms of all. It's a sensation that instinctively and urgently demands scratching.

But, in a cycle that adds insult to injury, the act of scratching can itself irritate the skin and lead to more scratching, thereby creating an itching-scratching-itching cycle.

Eventually, prolonged scratching and rubbing thickens and even scars the skin.

The medical name for itch is "pruritus", derived from the Latin prure, "to itch". The term has nothing to do with inflammation - otherwise it would be spelled 'itis' rather than 'itus'.

But pruritus is a rather pompous term, redolent of an era where doctors sought to impress rather than to demystify. Far better to use itch, descended from a perfectly good Old English word gyctha, the initial g having fallen out of use.

During my obstetrics training in one of Dublin's maternity hospitals, I looked after a pregnant woman who was unable to sit still such was the intensity of her itch. An all-over itch occurs in about 2 per cent of pregnancies.

It may be due to a pooling of bile in the gallbladder and liver. The only definitive cure is giving birth, which wasn't much consolation to our patient, who was 32 weeks pregnant.

Such was her level of distress she was admitted to hospital. Prescribing in pregnancy is best kept to a minimum, but this poor woman required sedation as she had been unable to sleep for a number of weeks. We also tried to control the temperature of her room to avoid overheating.

I'd like to think we made her more comfortable, but I'm not sure how successful we were given the prescribing restrictions posed by her unborn child.

Some years later, working as the medical director of a hospice homecare team, I saw how distressing itch can be for people with terminal cancer. It may be the result of high levels of bile salts in the blood, but itch seems to occur more often with certain cancers such as Hodgkin's disease, lymphomas and stomach tumours.

Several chemicals produced by the body cause itching; histamine being the classic. Itch and pain seem to be interlinked, so that hot or cold applications to the skin can stop an itch.

Brain scanning of people with deliberately induced itching showed that when they were allowed to scratch, areas of the brain associated with unpleasant sensations became less active, while areas associated with pain become more so.

Offering palliation to cancer patients with intractable itch involves a multi-faceted approach. Taking a cool or lukewarm bath, with sodium bicarbonate added to the water, helps relieve the all-over itch experienced by some cancer patients.

Alcohol and spicy food cause blood vessels near the skin to dilate, which may worsen the itch, and so are best avoided. It also helps to keep the temperature of the room cool, as overheating precipitates itch. And rough clothing or fabrics irritate an already sensitive skin.

Covering the skin with a cooling agent such as calamine or menthol lotions is useful. Most people with severe itch will also require oral medications.

Antihistamines are the first choice and choosing one with a sedating effect as a night-time dose will help the person sleep.

Old-fashioned antidepressant drugs such as amitryptalline, or anti-epilepsy medication such as gabapentin, may help to relieve itch that does not respond to more conventional measures.

Generalised itching without a rash, that comes on without an obvious cause, is rarely a sign of serious disease. But it can signal kidney failure as well as thyroid and liver problems.

Even more rarely, it could be a sign of an otherwise hidden cancer. So if you experience prolonged itching that cannot be attributed to an obvious cause, then it's best to see your doctor to have it checked out.

In most cases, the itch will turn out to be something benign and amenable to simple treatment.

And if you find it difficult not to scratch, console yourself with the words of the Chinese sage, Chang Ch'ao: "it is easy to stand a pain, but difficult to stand an itch".