Psoriasis is an immune-mediated incurable skin condition, which means there is no known cause, other than an incorrect immune response that leads to inflammation on the skin - raised plaques, silver scales etc. However, there are known triggers that can cause psoriasis to flare up, such as: cold and dry weather, injuries (scrapes, bug bites, sunburn), other auto-immune illnesses. There are also indications of factors that exacerbate the symptoms, such as: allergies, certain foods, alcohol and stress. The best way to learn about your triggers is to monitor flare-ups adn determine which factors were present at the time.