Image caption Researchers think it could be the barley in beer that increases the psoriasis risk

Women who drink beer regularly are more likely to develop the skin disease psoriasis, a US study suggests.

The study found that women who drank five beers a week doubled their risk of developing the condition compared with women who did not drink.

The Boston study, in Archives of Dermatology, looked at more than 82,000 female nurses aged 27 to 44 and their drinking habits from 1991 until 2005.

Non-alcoholic beer, wine and spirits were not found to increase the risk.

In the study, researchers said that woman who drank more than two alcoholic drinks a week increased their risk of psoriasis by two-thirds compared with non-drinkers.

For women who drank five glasses of beer per week their risk of developing psoriasis was 1.8 times higher again.

Women with a high risk of psoriasis may consider avoiding higher intake of non-light beer Dr Abrar Qureshi, Harvard Medical School

When stricter criteria were used to confirm psoriasis cases, their risk was increased 2.3 times.

Yet women who drank any amount of low- or non-alcoholic beer, white wine, red wine or spirits per week were not found to be at increased risk.

Barley content

Author Dr Abrar Qureshi, from Harvard Medical School, Boston, wrote in the journal: "Non-light beer was the only alcoholic beverage that increased the risk of psoriasis, suggesting that certain non-alcoholic components of beer, which are not found in wine or liquor, may play an important role in new-onset psoriasis."

The study suggests that it could be the gluten-containing barley, used in the fermentation of beer, which is the cause of the increased psoriasis risk.

Previous studies have shown that a gluten-free diet may improve psoriasis in patients who are sensitive to gluten.

People with psoriasis may have a so-called latent-gluten sensitivity, compared with people without psoriasis, says the study.

"Women with a high risk of psoriasis may consider avoiding higher intake of non-light beer," the authors conclude.

Psoriasis is a chronic skin disease characterised by itchy red scaly patches that most commonly appear on the knees, elbows and scalp but can show up anywhere, including the face.

The effects can range from mild to disfiguring enough to be socially disabling.