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 percent to 3 percent of the population develops 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

Stress can cause psoriasis to flare 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.

Medications

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 percent 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.

Infection

Anything that can affect the immune system can affect psoriasis. In particular, streptococcus infection (strep throat) is associated with guttate psoriasis. Strep throat often is associated with the first onset of guttate psoriasis in children. You may experience a flare-up following an earache, bronchitis, tonsillitis or a respiratory infection, too.

It's not unusual for someone to have an active psoriasis flare with no strep throat symptoms. Talk with your doctor about getting a strep throat test if your psoriasis flares.

Learn more about how psoriasis can affect your risk for infection »

Although scientifically unproven, some people with psoriasis suspect that allergies, diet and weather trigger their psoriasis. Strep infection is known to trigger guttate psoriasis.


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