Sunshine represses the body’s immune system

Press, 18 January 1986, Page 18

Sunshine represses the body’s immune system

By

KEITH HALLEY,

London Press science staff

Extensive and continuous exposure to the ultra-violet component of sunlight has long been identified as a possible cause of some skin cancers, but researchers at Edinburgh University’s department of bacteriology believe that the sun may have adverse effects in other health fields as well. Dr Mary Norval, a virologist, and Dr Sarah Howie, an immunologist have been working on the nature of “latent” skin infections — those which, once contracted tend to remain in the body indefinitely with their symptoms in some cases reappearing periodically. In particular, they have been looking at two very common viral skin infections, Herpes simplex, which often shows itself as reappearing cold sores around the mouth, and Papilloma, which produces warts.

“A great deal of research has been done on these viruses,” said Dr Norval, “and a lot is known about the effects of ultra-violet light. It not only produces a fine suntan, but also temporarily depresses the body’s immune system. However, nobody appears to have linked the study of these two areas of research together before.” Dr Norval and her team have been concentrating on some of the effects on the skin of shorter periods of exposure to sunlight — less than that required to produce burning of skin. “Our results so far show that the body’s normal immune response appears to be suppressed between the third and tenth day after ultraviolet irradiation. Therefore during the period, if someone’s skin is in contact with a foreign substance

or an infection which is clinically obvious, the person is vulnerable both to new infections and — if they already have a latent viral condition — to a recurrence of the obvious symptoms, such as cold sores.”

The basic research the group is undertaking, funded by Britain’s Medical Research Council, aims to isolate the cells which cause this suppression of the immune system. It is, however, already producing some pointers which could be useful in controlling such infections.

The group’s findings also appear to raise questions about whether the avoidance of certain environmental conditions might prove beneficial, and whether those who are affected should try and avoid contact with others who may be vulnerable to infection.