Active Ingredients.

Sunscreens have been traditionally divided into chemical absorbers and physical blockers based on their mechanism of action. Chemical sunscreens are generally aromatic compounds conjugated with a carbonyl group. These chemicals absorb high intensity UV rays with excitation to a higher energy state. The energy lost results in conversion of the remaining energy into longer lower energy wavelengths with return to ground state. Physical blockers reflect or scatter UVR.

Allowable ingredients as listed in the FDA monograph, as are maximum allowable concentrations, are shown in the table, along with their maximum allowable concentration. Sunscreen ingredients can also be classified by the portion of UVR they effectively absorb.

To view some of the above structures, please click here.

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