As far as I have been able to research I have found that there are two types of sunscreen: physical and chemical. The kind I use anthelios is chemical.
Chemical vs. Physical Sunscreens
Chemical Sunscreens are synthetic chemical substances with the following properties:
they are powerful absorbers of UV radiation
when they absorb radiation they remain relatively
These sun filters are formulated with other compounds in order to obtain highly effective products with protection factors varying from 4 to 30. Importantly, they often have to be reapplied quite frequently.
For many people, however, the advantages of chemical sunscreens outweigh the disadvantages. With all products it is advisable to read the label, to check that the product blocks both UVB and UVA radiation.
\tpreparations that can be used by small children. All should be reapplied after sweating or swimming, even if the product claims to be waterproof and rub-proof, or to offer 'all-day protection'. Ideally, whichever sunscreen you choose, make sure that it blocks both UVB and UVA and has a sun protection factor (SPF) rating of at least 15.
Slip, slap, slop
In Australia the Government and doctors led a public information program to reduce the effects of sun damage. They used the slogan 'Slip, slap, slop':
Slip on a tee-shirt, slap on a hat and slop on some sun cream.
Physical sunscreens contain inert mineral particles that reflect UV rays like a mirror. The most common type used is ultrafine titanium dioxide (TiO?), made up of minute particles only 20-30 mm? in size.
These products have advantages over chemical sunscreens in that they are inert substances that do not break down over time. They are far less liable to cause skin irritation, since they are in the form of insoluble particles that are not absorbed through the skin. Because of the small size of the particles, modern physical sunscreens reflect radiation in the UVB and short UVA regions better than earlier products did. Also, whereas their predecessors left a slight residue on the skin that looked like a trace of make-up base, which some people found unattractive, today's products have better transparency and avoid this problem.
There are formulations for use on the face and lips, and special preparations that can be used by small children. All should be reapplied after sweating or swimming, even if the product claims to be waterproof and rub-proof, or to offer 'all-day protection'. Ideally, whichever sunscreen you choose, make sure that it blocks both UVB and UVA and has a sun protection factor (SPF) rating of at least 15.
http://www.pg.com/science/skincare/S...DY0RCVQFIAJ1S0