Greg Flippin, age 13, of Springfield, Ore., for his question:
WHAT IS PHOTOSENSITIVITY?
The average person's skin is tough and can stand a lot of changes in temperature. A person with dry skin, however, suffers when there is a drop in the humidity level because there can be a painful loss of moisture from the skin. Oily skins, too, can cause special problems. And another type of problem exists when a person discovers he's sensitive to a change in the light.
When skin shows an exaggerated response or sensitivity to light, it is said to be photosensitive, and the condition is called photosensitivity.
Prerequisite for photosensitivity is the presence of a photosensitizing agent in the skin, followed by exposure to light. The usual source of light that produces photosensitivity reactions both indoors and outdoors is natural sunlight.
Common window glass doesn't filter out the rays of the sun responsible for some photosensitivity reactions. Some artificial light sources, including fluorescent tubes, can also cause reactions.
The skin reaction may consist of redness, itching, inflammation and rash. Some photosensitizers also produce skin discoloration or areas of brown spots. This condition is called hyperpigmentation.
Many agents found in a large number and variety of items can act as photosensitizers. Included are certain medications and foods as well as other items that come in contact with the skin. Among commonly used products that may contain photosensitizers are perfumes, some types of soaps, synthetic detergents, antiseptic creams, hair conditioners and some after shave products.
If the photosensitizing agent is identified and further is contact avoided, the skin condition usually improves rapidly. Unfortunately, in a few people it does not improve and may persist for months or years after the last known exposure.
As sunlight is usually the cause of photosensitive reactions, the photosensitive individual should avoid or minimize exposure to sunlight. Sun blocking lotions called sun screens as well as protective clothing provide some protection when exposure is unavoidable.
A number of colored lenses have been put to good use with sunglasses that protect the eyes from sun glare. A polarized filter can absorb some of the light, transmiting only a fraction. Sunglasses can also be made with special lenses that darken in the sunlight and become almost colorless indoors.
Safety glasses are used by factory workers to prevent fragments of metal from hitting the eye, while special glasses for arc welders cut off all harmful light rays.