All substances permitted for use in marketed
products are registered under regulated lists. Before
approval, these substances must first pass
many tests, including toxicology, in order to ensure
the greatest possible safety. These compounds
cannot penetrate the skin barrier and enter
systemic circulation nor penetrate into cells
where they could cause mutations in the cellular
DNA. Ideal UV protectants are non-toxic and do
not cause allergic reactions. Modern cosmetic
formulations are based on completely insoluble
compounds, which minimize the risk of a compound’s
penetration. Additionally, these preparations
contain more than one UV protectant compound
to ensure a wider-range of protection.
Most combine several compounds of different
chemical groups with different absorption maximums
in order to reduce the concentration of
each individual substance, hence, obtaining the
widest possible range of protection and improving
durability and stability by combining filters
fat-soluble and water-soluble filters. Increased
use of these compounds is the cause for allergic
reactions, mainly photoallergic contact dermatitis.
A study conducted in 2010 confirmed that the
compounds used as chemical filters were the
main allergens causing photoallergetic contact
dermatitis31
. Chemical filters with unstable molecules
can be inactivated by UV light, thereby,
losing protective ability. Accordingly, mixtures of
different UV-filters cannot be produced without
proper scrutiny, because there is the possibility of
negative interactions.