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UVA and UVB rays are most important radiations and have strange nature, because use in treatments for different diseases and causes many skin conditions like skin cancer etc.
For the treatment purpose special instrument are developed which emit uva or uvb light.
UVA UVB
Both uva uvb light rays are most hazardous for skin. uva is less dangerous as compare to uvb it damage deoxyribonucleic (DNA) indirectly and where as uvb light directly damage it.
In past the intensity of uva and uvb light was not so high as today, because of Ozone layer, this is the layer in outer atmosphere which can block uva and uvb rays and absorbs these in it. In current environmental situation thickness of ozone is continuously decreasing.
UVB light
uvb light is most hazardous ray for skin a big source of skin cancer. Due to his high frequency it is capable of damaging DNA. These are rays sunlight has tanning effects. This is reason that some time uvb rays called tanning rays.
It does not penetrate deeper into skin and affect epidermis (outer layer of skin).
When uvb light penetrate into skin it turns into energy. This is the reason that it causes tanning and when sun light contain sufficient amount of uvb light it causes burning in skin.
Strength of uvb light vary with passage of time almost in periodic way. That it is at its highest value at after noon hours. More in summer as compare to winter.
Wave length of uvb ranges from 285 to 315 nm.
UVB Treatment
UVB light is not only hazardous to health but use in several medical therapies for the cure of different disease and conditions.
It is specially used for the treatment of chronic skin conditions like vitiligo, psoriasis and eczema etc.
Vitiligo is a loss of pigmentation of skin. In treatment of vitiligo uvb treatment is used to enhance the pigmentation of skin.
In psoriasis growth and die cycle time of skin cells decreases to about 6 days. These dead cells instead of leaving skin, stuck up the skin surface. And an inflammation developed in skin. UVB is an effective treatment of skin and slow down the rapid growth of skin cells.
UVA Light
Normally it is considered as less destructive. It is right that it is less dangerous as compare to uvb light but an study shows that it also causes destruction of DNA but indirectly.
Density of uva light remain almost stable throughout the day. It ranges in wavelength 315 to 400 nm.
It causes brownish shade of skin when exposed to uva light. It is due to the uva that our skin becomes brown when exposed to uva light. Its energy and frequency is lower as compare to the uvb light. It is familiar regarding pre mature aging.
PUVA Treatment
I think it is the best utilization of uva rays. PUVA treatment technique consist of uva rays and sensitizing herb Psoralens. First psoralens are applied topically to the affected part of skin of the patients and then it is exposed to the uva light, emitting from a device specially developed for this purpose.
Note: technical info about uva and uvb is provided by http://www.antivitiligo.com/vitiligo-treatment/uvb.html
