DA Clinic

Sun Protective Agents
With increased attention to physical fitness and outdoor recreational activities,daily exposure to sunlight is common. As such,behavioral modification of seeking shade during peak ultraviolet B ( UVB) hours of 10:00A.M. to 4:00 P.M.and the use of photoprotective measures,such as sunscreen, clothing, wide-brimmed hat and sunglasses, have become the appropriate public health message to deliver.
Sun Protection Factor
By definition,SPF is the ratio of minimal erythema dose (MED) of subjects photoprotected skin over the MED of the unprotected skin.  Because the end point is erythema, predominately an effect of UVB exposure, the SPF value is mostly a reflection of the pretection against UVB radiation.
The concentration of sunscreen specified for SPF testion (2mg/cm2) is the equivalent of 1 oz(30 ml) of sunscreen to cover the entire body surface.
UV Filters listed in the U.S.Food and Drug Administration Sunscreen Monograph
1.Organic absorbers: UVB filters
2.Organic absorbers: UVA filters
3.Inorganic absorbers
Garments
Clothing as a photoprotective measure. Polyester fibers are the best UV absorber,whearas cotton and rayon are the poorest.Wetness decreases the UV-protection of a light colored (especially white)garment. The emission of visible light from the fabric makes the fabric look brighter.