Teenagers who spend more time outside in the sun have a lower risk of hay fever and eczema, according to a new study.
Those who spend more than four hours per day exposed to sunlight on summer days benefit from decreased rates of both conditions, Australian scientists found.
‘Higher sun exposure during summer holidays and summer weekends in adolescence was associated with significantly reduced eczema and rye grass positive rhinitis,’ they wrote.
Teenagers who spend more than four hours per summer day outside in the sun have a lower risk of developing hay fever and eczema but scientists do not know why this isThe team found that the benefit of sun exposure persisted after accounting for measured levels of vitamin D, the so-called sunshine vitamin which our body produces from sunlight on our skin, in participants.
This suggests the benefit stems from another mechanism, according to the researchers led by Dr Andrew Kemp at the Royal Children’s Hospital in Melbourne.
There are estimated to be more than 10 million people in England with hay fever, and grass pollen is by far the most common allergen.
Hay fever is more likely if there is a family history of allergies, including eczema.
More... Safe travels! New vaccine against 'Delhi belly' could end holiday misery for millions One in four angina patients 'get the wrong treatment': 'Flawed' test affects 25 per cent of those checked for the diseaseAround one in five children in the UK has eczema, according to NHS Choices. Although 65 per cent of cases clear up by the age of 16, severe eczema can have a major impact on quality of life.
The study involved 415 participants, who were recruited at birth and followed until the age of 16.
Their average daily duration of sun exposure in summer months was recorded at eight and 16 years of age.
At 16, researchers also recorded whether they suffered from hay fever, eczema, asthma or showed any signs of sensitisation to allergens.
Time spent in the sun as a child does not affect an adult's chance of developing hay fever and eczemaThere was no significant association between sun exposure aged eight and any allergic disease or allergen sensitisation at 16.
But teens who spent more than four hours per summer day in the sun aged 16 had a significantly decreased risk of hay fever and eczema.
Asthma was not related to sun exposure, whether assessed through diagnosis by a doctor or use of asthma medications.
The authors, whose findings are published in the online version of the journal Paediatric Allergy and Immunology, said the reasons for the protective effect of sunlight were not certain.
They said one possibility is that ultraviolet (UV) irradiation can have effects on the immune system that might impact on the development of allergies.
A number of previous studies have shown that UV exposure can suppress the immune system and inflammatory activities.
But this does not explain the effect on hay fever, where the site of inflammation is not directly exposed to UV light.
‘It is possible that cells modulated by UV, following migration from the skin to other organs, might produce effects elsewhere,’ they wrote.
‘It has also been suggested sun exposure by inducing antimicrobial peptides may enhance antibacterial defences. This could benefit diseases such as eczema where bacterial colonisation of the skin is considered to play a significant role.’
They called for further studies in the area to consider both exposure to UV rays and vitamin D before sun exposure is recommended to reduce rates of allergic disease.