These agents absorb mostly in the UVA region (320-350 nanommeter wavelength). Products that contain benzophenones can cause photocontact allergy to these agents. Contact-sensitivity has been reported with these compounds.
These compounds are capable of a high degree of UV absorption. However, they are also unstable, and can quickly undergo photo degradation into unprotective compounds.
New UVA blockers:
Examples of this type of sunscreen are ZINC OXIDE and TITANIUM DIOXIDE.
These contain particles that scatter, reflect or absorb solar radiation. However, the particles are large enough to make the sunscreen visible when applied, thus the white nose on the lifeguard, cricketers.
Newer micronized reflecting powders provide broad-spectrum protection against UV radiation and are more cosmetically acceptable because they are invisible when applied. Micronized titanium dioxide is chemically stable and does not cause photo allergic or contact dermatitis. It is also effective in blocking shorter UV wavelengths. Microfine zinc oxide is transparent on the skin and does not produce the opaque "pasty" color of zinc oxide with larger sizes.