Psoriasis is marked by scaly, itchy, occasionally painful rashes. Prescription medications — including steroid creams that ease inflammation — are far from perfect.
When over five million Americans suffer from that skin condition, any claims of permanent cure, can evoke frenzied response, especially when backed by some kind of evidence.
And that is what is happening to Skin Zinc, even though experts are skeptical.
"We can control psoriasis, but we can't cure it," says Dr. Steven Feldman, professor of dermatology at Wake Forest University. "People want something magical that will work without side effects."
The SkinZinc system — sold at major drugstores and over the Internet — combines two products: SkinZinc spray and SkinCylic cream. The active ingredient in the spray is a 0.25% solution of zinc pyrithione, the same active ingredient found in Head & Shoulders dandruff shampoo SkinCylic - the cream contains 2% salicylic acid, a common ingredient in both prescription and over-the-counter psoriasis treatments. The Walgreen's website sells 4 ounces each of the spray and the cream for about $40.
"Patients ask about SkinZinc very frequently," says Dr. Kenneth Gordon, assistant professor of dermatology at Northwestern University and a medical board member of the National Psoriasis Foundation. "I know I have many patients who have gone out and bought it."
Bernard Willimann, executive vice president for Preval Health, the Maine-based company behind SkinZinc, says that the system is the bestselling over-the-counter treatment for psoriasis in the U.S. and Canada. "Some people try it without success, but a lot of people are very loyal to it," he says. "Some of the letters and pictures we get are amazing."
In one radio spot, an unidentified customer calls it "the closest thing to a medical miracle." Ads in national magazines claim that the SkinZinc spray "goes on like water to help eliminate painful, stubborn symptoms, including itching, scaling, flaking, and redness."
Ads and product labels state that SkinZinc is effective for dandruff and seborrheic dermatitis (a relatively mild rash of the face, scalp or trunk) as well as psoriasis.
Skin products containing zinc have "been around forever," Gordon says, but there's no evidence that they help treat psoriasis. He suspects that a zinc spray might slightly ease inflammation and that it might be a bit more helpful for seborrheic dermatitis than for psoriasis.
But it's only a hunch, he adds, because zinc treatments have never been thoroughly studied. "I have a hard time espousing it, because there's no data on it."
The salicylic acid in the SkinCylic cream should help break down scales in the skin, he says, but the effect is strictly cosmetic. Neither the spray nor the cream have much potential to address the root causes of psoriasis, he says.
Zinc caused a brief buzz in dermatology circles in the late 1990s when patients started getting amazing results from a zinc product called Skin-Cap.
The excitement died when tests showed that the Spanish-made product also contained clobetasol propionate, an extremely potent topical steroid.
Topical steroids are available only on prescription and there are dangerous side effects to it including raised blood pressure, fluid retention, diabetes and suppression of the adrenal gland.
A 2003 study conducted by Feldman and colleagues suggests that the zinc in Skin-Cap deserved none of the credit for the product's healing powers. Twenty-four psoriasis patients were treated with either clobetasol alone or the steroid combined with a 0.25% zinc pyrithione spray.
Patients applied the products twice a day for two weeks. At the end of the study, the patches of skin treated with the zinc-steroid combination didn't look any better than the patches treated solely with steroids.
Gordon doesn't doubt that some people have enjoyed clearer skin after using the SkinZinc spray or other zinc products. Psoriasis can wax and wane for no obvious reason, he says, and about 5% of patients treated with nonactive placebos report dramatic benefits.
In Feldman's view, SkinZinc spray is probably not likely to do any good, but it won't do any harm, either.
The only danger, he says, is that patients using the spray might be missing out on therapy — including steroid creams — that could really help.