Cosmetic Conundrums

Q. Why does aloe vera gel work to soothe thermal burns?

A. Aloe vera gel can be obtained in commercial burn preparations or by cutting open the leaf of this succulent plant. The gel that oozes from the cut leaf is considered a mucilage - a thick, viscous, clear liquid. The mucilage is 99.5 percent water, with mucopolysaccharides, choline and choline salicylate making up the remaining 0.5 percent.

Furthermore, the aloe vera concentration may be too low to contain enough choline salicylate for a therapeutic effect. Better clinical results are probably obtained with fresh plant juice than commercial aloe vera preparations.

Q. How does N-acetyl glucosamine work in pigment lightening?

A. N-acetyl glucosamine has an established reputation as an oral supplement to improve joint pain in individuals with osteoarthritis. It has more recently been introduced as the active agent in a new line of anti-aging moisturizers (Olay Definity, Procter & Gamble). Cosmetic chemists have noted that n-acetyl glucosamine stimulates the synthesis of hyaluronic acid.

Hyaluronic acid is a humectant that holds water within the skin. It can be used topically to improve skin moisturization and reduce fine wrinkling due to dehydration. It can also be cross-linked and injected as a filler to reduce nasolabial folds.

N-acetyl glucosamine also inhibits the glycosylation of tyrosinase, a key enzyme in melanin production. For this reason, N-acetyl glucosamine is claimed to even skin tone by reducing brown dyspigmentation. With the potential loss of hydroquinone in the over-the-counter cosmetic market, manufacturers are looking for other ingredients that can produce pigment lightening.

Q. What is dimericine?

A. Dimericine (AGI Dermatics) is a new ingredient included in high-end cosmeceuticals to inhibit skin aging. It contains T4 endonuclease V, a substance important in DNA repair.

T4 endonuclease V functions to nick DNA strands for repair enzymes to remove photodamaged DNA. DNA photodamage repair is the only mechanism of photoprotection used by the body that has not been synthetically duplicated.

Inorganic sunscreen ingredients, such as zinc oxide and titanium dioxide, have been developed that scatter and reflect light like the stratum corneum. Organic sunscreen ingredients, such as avobenzone, oxybenzone, octyl methoxycinnamate, etc., have been developed that can absorb and convert UV radiation to heat like melanin.

DNA repair as a method of photoprotection, however, has not been previously available.

A Zoe Diana Draelos, M.D., is a clinical associate professor of dermatology, Wake Forest University School of Medicine, Winston-Salem, N.C., and primary investigator, Dermatology Consulting Services, High Point, N.C. Questions may be submitted via e-mail to zdraelos@northstate.net