Psoriasis is a chronic, non-contagious skin condition defined by patches of abnormal skin that are typically red, scaly, and itchy. It is not caused by an infectious organism, such as a fungus, but is instead an inflammatory disorder rooted in the immune system. The immune system mistakenly targets healthy skin cells, triggering inflammation and accelerated cell growth. While this long-term disease has no cure, various treatments can help manage symptoms and reduce flare-ups.
Psoriasis is Not a Fungus
The confusion between psoriasis and a fungal infection is common because both produce red, scaly patches on the skin. However, their underlying causes are fundamentally different, requiring distinct treatment approaches. Fungal infections, such as ringworm or athlete’s foot, are infectious conditions caused by organisms like yeast or mold. These infections are contagious, spread through contact, and thrive in warm, moist environments.
Psoriasis is not contagious and cannot be transmitted from person to person. It is classified as an autoimmune-mediated inflammatory disease, driven by the body’s own defense system. While both involve scaling, psoriatic scales are often thicker and silvery-white, distinct from the thinner scaling of many fungal rashes. Fungal infections are treated with anti-fungal medications, while psoriasis requires treatments that modulate the immune response and skin cell growth.
The True Cause of Psoriasis
Psoriasis is a systemic inflammatory disease driven by a dysregulated immune system. Specialized white blood cells called T-cells mistakenly activate and attack healthy skin cells. These T-cells release inflammatory signaling proteins, or cytokines, into the skin. This immune response leads to the hyperproliferation of skin cells, known as keratinocytes.
In healthy skin, cells grow and shed over a cycle of approximately 28 to 30 days. Psoriasis inflammatory signals accelerate this process, causing skin cells to reach the surface in three to seven days. Because cells are produced too rapidly, they pile up instead of naturally flaking off. This rapid buildup forms the thick, raised lesions, or plaques, that characterize the condition. Genetic factors play a significant role, but environmental triggers are necessary to initiate the immune system’s attack.
Common Manifestations and Triggers
Plaque psoriasis is the most common form, accounting for about 90% of cases. It is characterized by dry, raised patches of skin, or plaques, often covered in silvery-white scales. These lesions frequently appear on the elbows, knees, scalp, and lower back. Other types include guttate psoriasis, which presents as small, drop-shaped spots, and inverse psoriasis, which affects skin folds.
While the disease is chronic, various factors can provoke a flare-up. Infections, particularly strep throat, are a trigger for guttate psoriasis. Injury to the skin, such as a cut or scrape, can cause new lesions to form in that area, known as the Koebner response. Other common triggers include high stress, heavy alcohol consumption, smoking, and the use of certain medications, such as lithium or some high blood pressure drugs.
Managing Psoriasis Symptoms
Treatment aims to interrupt the inflammatory cycle, slow skin cell growth, and alleviate symptoms. For mild to moderate cases, topical treatments are the first approach. These include creams and ointments containing corticosteroids to reduce inflammation, or vitamin D analogs and retinoids to normalize skin cell turnover. Topical treatments are applied directly to the affected skin to manage localized patches.
When the disease is widespread or severe, or does not respond to topical therapy, doctors may introduce phototherapy or systemic treatments. Phototherapy involves exposing the skin to specific wavelengths of ultraviolet light, such as narrowband UVB, which slows cell production and suppresses the immune response. Systemic therapies are oral or injectable medications that work throughout the body to target the root cause of the inflammation. This category includes traditional immunosuppressants like methotrexate and biologic medications that target specific inflammatory proteins.