The Sunscreen Filter
may be effective in treating acne and reducing melanin production and oxidation. 24 Moreover, topically applied vitamin
C stability has been demonstrably increased by addition of other antioxidants
to the solution, including vitamins E and
ferulic acid. 25
A chronic effect of the depletion of the
primary antioxidants, viz., the E vitamins
and vitamin C, in surface epidermal layers is the reduction of overall antioxidant
capacity within the skin and consequent
depletion of other vital antioxidant molecules in the epidermis, leading to intrinsic antioxidant defense system failure. 26
Because the skin constitutes the primary
barrier against pollution, topical application of properly formulated antioxidants
for optimal penetration is a very effective
strategy to overcome the pollution and age
related depletion of cutaneous antioxidants. Ongoing industry research suggests
topical antioxidant formulations show potential to both prevent and repair the pol-lution-induced oxidative stress in the skin.
However, far more research is needed to
define the precise molecular mechanisms
behind the damaging effects of pollution
and ways to quantify the protective benefits offered by topical products.
In conclusion, the skin is the human
body’s largest organ, comprising some
16 ft2 to 22 ft2 of epidermis, dermis, and
hypodermis and up to 50% of the body’s
fat and, as such, any factors affecting the
skin’s health will impact the body’s health
as a whole. This two-part review has illustrated that air pollution is ubiquitous and
exercises a surprisingly extensive effect on
human skin health, in particular:
1. The transdermal absorption of
alarmingly large quantities of pre-radicals,
sometimes accounting for 50%, or more,
of bloodstream content of these substances, as compared to the amount(s) derived
2. Ozone-based depletion of endogenous antioxidants; viz., vitamins E, and
consequent depletion of vitamin C;
3. In synergy with UV photo-oxidative
mechanisms to deplete epidermal surface
vitamin C and vitamins E levels; as well as
4. Interacting with UV radiation to
photoconvert air pollutant-derived dermally absorbed pre-radicals into active
These air pollution insults on human
skin, with or without UV-complicit exacerbation, which, if not treated, will not
only result in serious chronic skin pathologies, such as cancer or loss of epidermal
barrier function, but will ultimately result
in organismal antioxidant defense system failure. Therefore, antioxidant countermeasures are necessary to ameliorate
these insults to skin health.
The most effective countermeasures
are topical applications of antioxidants to
the skin at the point of insult. Vitamin C
and E vitamins are the most prominent
candidates as ingredients in such applica-
tions because they are:
• Two of the primary antioxidants in
• Easily obtainable from several sourc-
• Effectively absorbed into the skin,
under appropriate conditions.
Thus effective topical antioxidant formulations designed for dermally absorbed
air-pollutant skin protection should include both vitamin C and E vitamins, both
stabilized with additional antioxidants and
photoprotective sunscreens, with vitamin
C being the more effective photoprotec-tant in the UVA range, and E vitamins being more effective in the UVB range, are
absorbed into different areas of the skin,
with the E vitamins absorbing into the
lipid-phase compartments and vitamin
C into the aqueous-phase compartments
and mutually stabilize each other.
I would like to thank Mustapha El Kouni
for the extensive research and support in
writing these two columns.
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Evidence”. Percutaneous Absorption; Mechanisms-Methodology-Drug Delivery, pp. 17-42. (R. Bronough
and H.I. Maibach [Eds.]). Marcel Dekker, New York,
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