Psoriasis is more than simply dry skin—it is a medical condition that affects over 3 percent of Americans, or approximately 5 million people. Psoriasis is an autoimmune disorder in which the brain mistakenly sends signals to the body to produce more skin cells than are needed; cells become so active that the individual's immune system is triggered, and the result is reddened, inflamed skin.

Topical treatments—those placed directly on the surface of the skin—are available in a variety of preparations, including lotions, creams and ointments. Lotions contain oil and alcohol in water and can be drying depending on the alcohol content. Creams are also made with oil in water, but they often have preservatives that can lead to allergic reactions. Ointments are semisolid preparations that are greasy and slower to absorb.

Applying standard hand lotions and beauty ointments has little effect on easing the discomfort of a flare-up of psoriasis. In order to be effective, a treatment must contain ingredients to slow the growth of skin cells—thereby reducing inflammation—and remove buildup of scales.

Over-the-Counter Lotions and Creams

Depending on the severity and location of the psoriasis, many cases can be treated with over-the-counter preparations. Two ingredients have been approved by the U.S. Food and Drug Administration for treatment of psoriasis: salicylic acid and coal tar. Both may be used on the body, hands, feet and scalp.

Salicylic acid causes the outer layer of skin to shed. It lifts and softens scales caused by psoriasis, helping to remove scales. Strong salicylic acid creams can be irritating to the skin if left on too long, and can occasionally weaken hair shafts and lead to hair loss. It should not be used on extensive areas of the body.

Coal tar slows the rapid growth of skin cells, decreasing inflammation, itching and scaling. The tar is applied once daily for 10 to 15 minutes. Though it can be highly effective for mild-to-moderately severe cases of psoriasis, there are a number of drawbacks to consider. Tar can irritate and dry the skin, so it should be tested on a small area first. Tar can stain clothing, bedding and even light-colored hair and makes skin highly sensitive to sunlight. Care must be taken to thoroughly wash off the tar preparation and to use sunscreen before going outdoors. Some studies have shown that tar preparations can cause cancer; however, according to the National Psoriasis Foundation, the FDA has determined that preparations containing 0.5 to 5 percent tar are safe.

Nonsteroidal Ointments and Creams

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Prescription nonsteroidal preparations include calcipotriene, tazarotene and anthralin.

Calcipotriene, or Dovonex, carries properties similar to vitamin D. It was developed after research showed that individuals with low levels of calcium and vitamin D were susceptible to psoriasis. According to Dr. Daniel Federman, Dr. Catherine Froelich and Dr. Robert Kirsner, in American Family Physician, it is a first-line treatment for psoriasis with few side effects, though it should not be applied to the face or groin area and should not be used by pregnant women.

Tazarotene has properties similar to vitamin A. Because it frequently causes dermatitis, tazarotene must only be applied to affected skin. It may also cause sensitivity to sunlight. It may be used on the face as well as the body. Tazarotene can cause birth defects and must not be taken by pregnant women.

Anthralin originated from goa powder, traditionally used for skin diseases in India and Brazil. Anthralin inhibits cell growth and is a very effective treatment for psoriasis but has drawbacks that have led to decreased use in recent years. Like coal tar, anthralin stains clothes, bedding and hair as well as skin and nails. It is very irritating to skin so must be applied with care. Petroleum or zinc oxide ointment may be applied around the affected skin to create a protective barrier.

Corticosteroid Treatments

Topical corticosteroids are the most-commonly used treatment for psoriasis. These steroidal ointments and creams are not the same as steroids used by bodybuilders—they are derived from the natural corticosteroid hormone produced by the human body and are highly effective in reducing inflammation and redness.

Low-strength corticosteroids are used on sensitive areas of skin, such as the face and genitals. Mid-strength preparations are used on the torso, arms, legs, hands and feet. Low- and mid-strength corticosteroids should be used for no longer than three weeks. The highest-strength corticosteroids should be used for no longer than two weeks and only on areas resistant to previous treatment or on the palms of the hands and soles of the feet.

Corticosteroids carry numerous potential side effects, including skin damage, easy bruising, skin thinning and changes in skin pigmentation. They can also cause damage to internal organs if applied to large areas or used for long periods, and can lead to cataracts or glaucoma, so corticosteroids should not be used around the eyes.