The Economist comments on how researchers believe a skin disease may trigger a lung complaint.

Common in wealthy countries, absent from poorer nations, the exact cause of asthma remains unknown.

Explanations range from clean modern living making the immune system over-reactive to random allergens to chemicals in swimming pools.

But researchers at Washington University in St Louis now suspect asthma is caused by a chemical distress signal produced in skin damaged by another hazard of modern life: eczema.

It is on the rise and in the same countries where asthma is a problem, though is not as dangerous and where many people with eczema go on to develop asthma.

Writing in the Public Library of Science Biology, the researchers now believe the culprit is thymic stromal lymphopoietin (TSLP), a signalling molecule “secreted by damaged skin cells which elicits a strong immune response from the body to fight off invaders.”

They hypothesise that eczema-induced TSLP enters the bloodstream and, when it arrives at the lungs, sensitises them so they react to allergens that would not previously have bothered them…they become asthmatic.

This was tested in mice, which also developed asthma.

Using genetic engineering, when they deleted the gene for the receptor molecule which picks up TSLP in the lungs the mice no longer developed asthma.

Findings that skin damage create susceptibility to asthma by releasing TSLP, at last offers a way to prevent asthma.

This indicates that eczema should be treated earlier while in the longer term, it might be possible to devise drugs that inhibit the production of TSLP.

Better still would be to work out what aspect of modern life causes eczema.