Scientists have opened the door to a new treatment for eczema that mimics the soothing benefits of sunlight on symptoms.
As well as being a good source of vitamin D, basking in the sun releases nitric oxide a molecule that reduces the inflammation behind itches, research found.
People with severe eczema are often prescribed tanning lamps to ease irritation, but this can cause burning, ageing of skin and even cancer.
Tests by the University of Edinburgh found exposing a small patch of volunteers' skin to UV light released nitric oxide into the bloodstream.
The chemical activates specialised immune cells, called regulatory T cells, which dampen inflammation.
It means treatments could be developed without the risks attached to light therapy.
The skin condition affects one in five children and 5 per cent of adults in Britain.
Lead researcher Dr Anne Astier, of the University of Edinburgh, said: Our findings suggest that nitric oxide has powerful anti-inflammatory properties and could offer an alternative drug target for people with eczema.'
The study was published in the Journal of Allergy and Clinical Immunology.