Psoriasis is one of the most complicated diseases in dermatology. No one knows what causes psoriasis, although scientists think it is a result of several factors including genetics, environmental factors, and the immune system.
Scalp Psoriasis is not contagious, but usually affects other parts of the body—although it may not always be present. Scalp psoriasis can be mild and almost unnoticeable or extreme, covering most of the scalp and extending to the face, back of the neck and ears.
Other skin disorders, such as seborrheic dermatitis, may look similar to psoriasis. However, scalp psoriasis appears powdery with a silvery sheen, while seborrheic dermatitis appears yellowish and greasy.
The U.S. Food and Drug Administration (FDA) has approved two drugs, Protopic and Elidel, for the treatment of eczema which many dermatologists have found work well for treating psoriasis on the face or other sensitive areas. Medication used to treat facial psoriasis should be applied carefully and sparingly; creams and ointments can irritate eyes. Because facial skin is delicate, prolonged use of steroids may cause it to become thin, shiny and/or prone to enlarged capillaries. A careful treatment schedule will ensure steroid treaments are safe.
Psoriasis Causes and Known Triggers
Scientists believe that at least 10 percent of the general population inherits one or more of the genes that create a predisposition to psoriasis. However, only 2 to 3 percent of the population develop the disease. Researchers believe that for a person to develop psoriasis, the individual must have a combination of the genes that cause psoriasis and be exposed to specific external factors known as "triggers". Read more about the science of psoriasis »
Psoriasis triggers are not universal. What may cause one person's psoriasis to become active, may not affect another. Established psoriasis triggers include:
Stress can cause psoriasis to flare up for the first time or aggravate existing psoriasis. Relaxation and stress reduction may help prevent stress from impacting psoriasis.
Injury to skin
Psoriasis can appear in areas of the skin that have been injured or traumatized. This is called the Koebner [KEB-ner] phenomenon. Vaccinations, sunburns and scratches can all trigger a Koebner response. The Koebner response can be treated if it is caught early enough.
Certain medications are associated with triggering psoriasis, including:
- Lithium: Used to treat manic depression and other psychiatric disorders. Lithium aggravates psoriasis in about half of those with psoriasis who take it.
- Antimalarials: Plaquenil, Quinacrine, chloroquine and hydroxychloroquine may cause a flare of psoriasis, usually 2 to 3 weeks after the drug is taken. Hydroxychloroquine has the lowest incidence of side effects.
- Inderal: This high blood pressure medication worsens psoriasis in about 25 to 30 percent of patients with psoriasis who take it. It is not known if all high blood pressure (beta blocker) medications worsen psoriasis, but they may have that potential.
- Quinidine: This heart medication has been reported to worsen some cases of psoriasis.
- Indomethacin: This is a nonsteroidal anti-inflammatory drug used to treat arthritis. It has worsened some cases of psoriasis. Other anti-inflammatories usually can be substituted. Indomethacin's negative effects are usually minimal when it is taken properly. Its side effects are usually outweighed by its benefits in psoriatic arthritis.
Although scientifically unproven, some people with psoriasis suspect that allergies, diet and weather trigger their psoriasis. Strep infection is known to trigger guttate psoriasis.