There are several contributing factors that can increase the risk of psoriasis either by acting as triggers or causing flare-ups:

Psoriasis gets its start in the epidermis, the skin’s dry outer layer. Immature skin cells develop deep in the epidermis. These cells are called keratinocytes because they produce keratin, a tough protein that’s an essential component of hair, nails and skin. In their normal life cycle, keratinocytes take about a month to mature and migrate from the bottom of the epidermis to the surface, where eventually they are discreetly shed.

 

In psoriasis, a faulty immune system sends signals that cause the normal turnover of skin cells to speed up tremendously, compressing the whole cycle into 3-5 days. The skin cannot shed these new cells fast enough, so they build up into thick, crusty patches. In the most common type of psoriasis, silvery, flaky areas of dead skin collect on the patches’ surface and are shed continuously.

 

Underneath the epidermis lies the dermis, the skin’s moist inner layer, which has many nerve fibres and blood and lymph vessels running through it. This network not only provides nourishment for the fast-developing skin cells but also, for unknown reasons, incorrectly floods the transitional layer between the dermis and epidermis with large numbers of T-cells. These immune-system cells release factors that cause the tissues beneath the psoriatic crusts to redden and become inflamed. Consequently, psoriasis can be painful, extremely itchy and can cause intense burning.