The cause of psoriasis isn't fully known, but it's thought to be related to an immune system problem with cells in your body. More specifically, one key cell is a type of white blood cell called a T lymphocyte or T cell. Normally, T cells travel throughout the body to detect and fight off foreign substances, such as viruses or bacteria. If you have psoriasis, however, the T cells attack healthy skin cells by mistake, as if to heal a wound or to fight an infection.
Overactive T cells trigger other immune responses. The effects include dilation of blood vessels in the skin around the plaques and an increase in other white blood cells that can enter the outer layer of skin. These changes result in an increased production of both healthy skin cells and more T cells and other white blood cells. This causes an ongoing cycle in which new skin cells move to the outermost layer of skin too quickly — in days rather than weeks. Dead skin and white blood cells can't slough off quickly enough and build up in thick, scaly patches on the skin's surface. This usually doesn't stop unless treatment interrupts the cycle.
Just what causes T cells to malfunction in people with psoriasis isn't entirely clear. Researchers have found genes that are linked to the development of psoriasis, but environmental factors also play a role.
Psoriasis typically starts or worsens because of a trigger that you may be able to identify and avoid. Factors that may trigger psoriasis include:
Apr. 11, 2014
- Infections, such as strep throat or skin infections
- Injury to the skin, such as a cut or scrape, bug bite, or a severe sunburn
- Cold weather
- Heavy alcohol consumption
- Certain medications — including lithium, which is prescribed for bipolar disorder; high blood pressure medications such as beta blockers; antimalarial drugs; and iodides.
- Bolognia JL, et al. Dermatology. 3rd ed. Philadelphia, Penn.: Saunders Elsevier: 2012. https://www.clinicalkey.com. Accessed Dec. 6, 2013.
- Longo DL, et al. Harrison's Online. 18th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=4. Accessed Dec. 6, 2013.
- Papadakis MA, et al. Current Medical Diagnosis & Treatment 2013. 52nd ed. New York, N.Y.: The McGraw-Hill Companies; 2013. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=1. Accessed Dec. 6, 2013.
- Psoriasis. National Institute of Arthritis and Musculoskeletal and Skin Diseases. http://www.niams.nih.gov/Health_Info/Psoriasis/.Accessed Dec. 8, 2013.
- Weigle N, et al. Psoriasis. American Family Physician. 2013;87:626.
- Feldman SR, et al. Epidemiology, clinical manifestations, and diagnosis of psoriasis. http://www.uptodate.com/home. Accessed Dec. 6, 2013.
- Armstrong AW, et al. The association between psoriasis and obesity: A systematic review and meta-analysis of observational studies. Nutrition and Diabetes. 2012;2:1.
- Korman N. Comorbid disease in psoriasis. http://www.uptodate.com/home. Accessed Nov. 16, 2013.
- Azfar RS, et al. Increased risk of diabetes mellitus and likelihood of receiving diabetes mellitus treatment in patients with psoriasis. Archives of Dermatology. 2012;148:995.
- Armstrong AW, et al. Coronary artery disease in patients with psoriasis referred for coronary angiography. American Journal of Cardiology. 2012;109:976.
- Ahlehoff, et al. Psoriasis and risk of atrial fibrillation and ischaemic stroke: a Danish nationwide cohort study. European Heart Journal. 2012;33:2054.
- Yeung H, et al. Psoriasis severity and the prevalence of major medical comorbidity: A population-based study. JAMA Dermatology. 2013;149:1173.
- Wan J, et al. Risk of moderate to advanced kidney disease in patients with psoriasis: population based cohort study. BMJ. 2013;347:1.
- Papoutsaki M, et al. Treatment of psoriasis and psoriatic arthritis. Biodrugs. 2013;27:3.
- Feldman SR, et al. Treatment of psoriasis. http://www.uptodate.com/home. Accessed Dec. 6, 2013.
- Almutawa F, et al. Systematic review of UV-based therapy for psoriasis. American Journal of Clinical Dermatology. 2013;14:87.
- De Migeul R, et al. Efficacy, safety, and cost of Goeckerman therapy compared with biologics in the treatment of moderate to severe psoriasis. International Journal of Dermatology. 2009;48:653.
- Garcia-Perez ME, et al. New therapies under development for psoriasis treatment. Current Opinion in Pediatrics. 2013;25:480.
- Korteum KR, et al. Results of Goeckerman treatment for psoriasis in children: A 21-year retrospective review. Pediatric Dermatology. 2010;27:518.
- Aloe. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed Dec. 9, 2013.
- Fish oil. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed Dec. 9, 2013.
- Oregon grape. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed Dec. 9, 2013.