"a sunscreen" is a correct and usable phrase in written English.
For example, "I always make sure to apply a sunscreen every morning before going outside."
I use a sunscreen with S.P.F. 15, sometimes 30.
She recommends daily, year-round use of a sunscreen.
A nanoparticle of titanium dioxide in a sunscreen could be as small as 15 nanometers.
Dermatologists recommend the routine daily use of a sunscreen with an S.P.F.
The American Academy of Dermatology, www.aad.org, has recently started a sunscreen "seal of recognition" program.
The SPF says nothing about how well a sunscreen protects against UVA light.
The orange, she explained, acts as a sunscreen, protecting the green layer underneath.
1988 The F.D.A. approves a sunscreen product containing avobenzone, a UVA-only filter.
Ozone concentrates high in the atmosphere, and acts like a sunscreen, absorbing harmful ultraviolet radiation.
It conditions and nourishes sun-parched skin and feels more like a moisturiser than a sunscreen.
