Aside from an association with some immune system genes, the reason an individual gets psoriasis is not known. Studies to date have investigated the role of bacteria, viruses, and environmental triggers without conclusive answers. Although the questions “Why me?” or “Why anyone?” can’t be answered at this time, no action, or lack of action currently identified, can control whether psoriasis appears. Many influences such as stress, medications, and skin trauma are known to exacerbate psoriasis, yet none of these influences by themselves or in combination are known to cause psoriasis. The initial triggers for psoriasis are not known and are not preventable at this time. Mitigating stress is a challenging project, but one that is known to help psoriasis and many other autoimmune diseases.
Many scientists have tried to pinpoint the immuno-logic trigger that begins the psoriasis process. Some researchers believe that a bacterial protein or fungus may be a trigger, and others believe that skin trauma may instigate and worsen psoriasis. No one entity appears to be the culprit in the majority of cases, and at this point, none of these theories have been proven or disproved.
One exception is guttate psoriasis, especially in children. This less common type of psoriasis may be triggered by a skin, throat, or ear infection, usually with the Streptococcus bacteria, commonly known as “strep.” Guttate psoriasis sometimes resolves with treatment of the initial infection. Guttate psoriasis triggered by an infection is usually distinctive because of the specific pattern of small (0.25 to 0.5 inch [0.5 to 1.0 cm] in diameter) spots all over the body, usually appearing in childhood or young adulthood. Some people who have had guttate psoriasis will go on to develop the more common form of plaque psoriasis.