Researchers from Washington University have finally hit upon the reason why young children who get a severe skin rash (eczema/atopic dermatitis) develop asthma and other breathing problems later.
The doctors call this progression the atopic march.
In the new study, researchers have shown that a substance secreted by damaged skin circulates through the body and triggers asthmatic symptoms in allergen-exposed laboratory mice.
Early treatment of skin rash and inhibition of the trigger substance might block asthma development in young patients with eczema.
"Over the years, the clinical community has struggled to explain atopic march," said study author Dr Raphael Kopan, professor of developmental biology and of dermatology.
"So when we found that the skin of mice with an eczema-like condition produced a substance previously implicated in asthma, we decided to investigate further.
"We found that the mice also suffered from asthma-like responses to inhaled allergens, implicating the substance, called TSLP, as the link between eczema and asthma," he added.
The researchers found that cells in damaged skin can secrete TSLP (thymic stromal lymphopoietin), a compound capable of eliciting a powerful immune response.
And because the skin is so effective in secreting TSLP into the blood system, the substance travels throughout the body. When it reaches the lungs, it triggers the hypersensitivity characteristic of asthma.
"We are excited because we've narrowed down the problem of atopic march to one molecule," said Kopan.
"We've shown that skin can act as a signalling organ and drive allergic inflammation in the lung by releasing TSLP. Now it will be important to address how to prevent defective skin from producing TSLP. If that can be done, the link between eczema and asthma could be broken," he added.
The findings are published in Public Library of Science Biology.