Eczema's link to asthma uncovered
Scientists believe they
have found what triggers many children with eczema to go on to develop
The Public Library of Science Biology study points to a way to stop what
is known as the "atopic march".
The US team at the Washington University School of Medicine showed that
a substance made by the damaged skin triggered asthma symptoms in mice.
The same substance,
thymic stromal lymphopoietin (TSLP), is also produced in the lungs of
Early treatment of the skin rash and blocking TSLP production might stop
asthma developing in young patients with eczema, they hope.
Drugs that act on TSLP might also protect against asthma development
even in cases that are not linked to eczema.
Allergies and asthma often occur together. Studies show that 50-70% of
children with severe allergic skin problems - atopic dermatitis - go on
to develop asthma.
The researchers studied mice bred with a genetic defect that made them
develop a condition similar to eczema in humans.
The defective skin secreted TSLP, which the researchers believe alerts
the body that its protective barrier has failed.
When they tested the lungs of the mice, they found this tissue also
responded strongly to the TSLP signal and had the hallmark traits of
asthma - mucous secretion, airway muscle contraction and invasion of
white blood cells.
They did more experiments and found that even mice with normal skin but
bred to overproduce TSLP also developed asthma-like symptoms, suggesting
TSLP is indeed the culprit.
Lead researcher Dr Raphael Kopan said: "We are excited because we've
narrowed down the problem of atopic march to one molecule.
"We've shown that the 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."
Dr Elaine Vickers of Asthma UK said: "This is the first piece of
research to suggest that the natural protein TSLP could play a direct
role in causing people with eczema to develop asthma.
"These results were obtained from studies with mice, so it is important
to establish whether the same causal link exists in humans.
"Scientists are already exploring the potential of targeting TSLP to
create new treatments for eczema, asthma and other allergic conditions.
"Although it is still a long way off, this research raises the exciting
possibility that as well as improving symptoms, these treatments might
be able to limit, or even prevent, the development of asthma."