Topical antioxidants can improve skin

The problem, she says, is that the marketplace is better at delivering hype than performance. Many commercial products contain ineffective antioxidants. Indeed, scientists have verified only a few as photoprotective - most prominently, vitamin C, vitamin E, ferulic acid, genisten, L-selenomethionine and silymarin.

If getting the right vitamin is the first step, the second is selecting the appropriate version of that vitamin.

For example, only one out of 32 vitamin E isomers (d-alpha-tocopherol) truly protects the skin from exposure to UV radiation. The concentration should be at least 2 percent. Vitamin C needs to be ascorbic acid in concentrations exceeding 10 percent.

"The final step," Dr. Burke says, "is developing a formula that maintains stabilized activity of these often labile antioxidants."

The best products put synergy to work. Cosmeceuticals with both C and E are four times as effective against photoaging than is either vitamin alone. Add ferulic acid and the protection is eightfold.

"I only know of a few companies worldwide - La Roche Posay, SkinCeuticals and Helena Rubenstein - that market effective forms of vitamin E and C in adequate concentrations," the dermatologist notes.

Antioxidants and photoaging

Having done independent research on topical antioxidants for many years, Dr. Burke says the skin's primary job is to protect the body from environmental stressors, such as the sun, cigarette smoke and air pollution.

These stressors trigger chemical reactions that produce free radicals.

But why use topical versions of antioxidants, since oral vitamins are much cheaper? It's the only way to get high concentrations in the skin. Direct application increases the epidermal concentration of vitamin C by a factor of 20 to 40 and the concentration of vitamin E by a factor of 10. This reservoir of photoprotection will persist in the skin for days. The more replete the skin is with antioxidants, the better its job performance in limiting and reversing the damage caused by free radicals.

Antioxidants and retinoids

"Antioxidants prevent photodamage primarily in the epidermis, while retinoids fight free radical damage primarily in the dermis," Dr. Burke says.

That's one reason combination therapy is important. Another is that retinoids and antioxidants prevent photoaging by different mechanisms, leading to better overall results.

"Vitamin C is very effective as a bleaching agent," Dr. Burke says. "A 15 percent to 20 percent solution will start working within one to two months."

Finally, antioxidants can do some things that are beyond the scope of retinoids. Creams and gels formulated with vitamin E, for example, can reduce transdermal water loss.