What ticked off its onset?

Psoriasis is considered to be an auto-immune condition in which the immune cells of the body mistakenly attack the body's own skin cells. This triggers an abnormal response in which there is abnormally fast growth of the cells leading to thickened skin & excessive shedding of the scales.

What triggers the auto-immunity cannot be exactly pin-pointed. However, auto-immunity tends to run in families and a genetic background has been verified in many cases over and over. There may be a family history of any kind of auto immune disease in the patient's family, not necessarily of psoriasis.

In addition many triggers have been identified that can initiate an attack of psoriasis. This may be in people who have never had at attack ever as well as people who suffer from the disease but are in remission. These external stressors serve as triggers for the inherited defect in immune function. They may even worsen the existing symptoms and some of the common ones are:

Bacterial infection such as streptococcal throat infection; thrush; viral infection

Stress - this is one of the commonest triggers for the abnormal immune response that is initiated in the body

Injury to the skin – this could be in the form of a cut, scrape, insect bite - the phenomenon in which the skin lesions occur at the site of the trauma is called Koebner phenomenon

Cold weather - the onset of winters is known to cause a relapse in a large number of patients of psoriasis

Environmental factors - sunburn, chemical burns, etc

Smoking

Excessive consumption of alcohol

A reaction to a vaccine

Certain medications – those containing lithium (found in some anti-depressants); beta blockers (high blood pressure medications); hydroxychloroquine (antimalarial drug); iodides