Psoriasis is neither infectious nor contagious. Injury to the skin commonly precipitates the appearance of psoriatic lesions. If the skin is cut, scratched, rubbed or severely sunburned, a flare-up often will occur 10 to 14 days after the skin is irritated. General health factors may influence psoriasis. Many patients note flare-ups of the disease during physical and emotional stress.
Infections can aggravate psoriasis.
Frequently, a flare-up of the disease can be triggered by severe viral or bacterial infections of the upper respiratory track. This has been particularly true following severe streptococcal infections of the throat. Psoriasis can also be triggered by certain drugs, including lithium and propranolol. Lastly, changes in the seasons can cause a variation in the severity of psoriatic lesions. This is less of a factor in the South where the seasonal change is not as pronounced as other climates.