Psoriasis is a common, chronic skin condition that often produces thick, red, scaly patches. The inflamed appearance of the skin can sometimes cause people to wonder if the problem is a fungal infection. Understanding the fundamental difference between these two types of skin issues is necessary for getting the correct diagnosis and effective care.
Psoriasis is Not a Fungus
Psoriasis is definitively not caused by a fungus, nor is it caused by any other type of external microbe like a bacterium or a virus. The condition is a disorder that originates from internal processes within the body, specifically involving the immune system. Psoriasis is a non-contagious condition, meaning it cannot be caught from another person or spread through contact. The skin changes seen in psoriasis are a reflection of an internal malfunction, in sharp contrast to infections, which require an outside infectious agent to invade the body.
Defining Psoriasis as an Autoimmune Condition
Psoriasis is classified as an immune-mediated disease, where the body’s protective mechanisms mistakenly target healthy tissue. White blood cells called T-cells become overactive and begin signaling the skin cells to multiply at an extraordinarily rapid pace. These T-cells trigger an inflammatory cascade in the skin. This misdirected attack leads to the release of inflammatory chemical signals, such as various interleukins, which perpetuate the cycle of inflammation and excessive skin growth.
In a person without psoriasis, skin cells grow deep in the epidermis and gradually rise to the surface over approximately one month, where they are shed naturally. With psoriasis, this entire life cycle is dramatically accelerated to occur in only three to seven days. The skin cells move to the surface so quickly that they do not have time to mature properly, resulting in a buildup of cells on the skin’s surface. This rapid accumulation of immature skin cells forms the thick, raised, scaly plaques characteristic of the condition.
Understanding Skin Mycoses
In contrast to psoriasis, a skin mycosis is a true infection caused by a fungus, which is a type of external pathogen. These infections are commonly caused by yeasts or molds, such as dermatophytes, responsible for common ailments like ringworm and athlete’s foot. Dermatophytes thrive by consuming keratin, a protein found in the outer layer of skin, hair, and nails. The fungi colonize these superficial tissues and grow outward, using the body’s own material as a food source.
Unlike psoriasis, these fungal infections are contagious and can be transmitted from person-to-person, from animals, or from contaminated environments. The fungi invade the skin from the outside and multiply, often causing a characteristic circular or ring-like rash as the infection spreads. This external, infectious origin represents a fundamental biological difference from the internal, non-infectious nature of psoriasis.
The Difference in Treatment Approaches
The distinct causes of psoriasis and skin mycoses demand completely different treatment strategies. Since fungal infections are caused by an external organism, their treatment involves antifungal medications designed to directly kill the invading fungus. These treatments work by targeting structures within the fungal cell, such as the cell wall or cell membrane, to stop the organism from growing or to destroy it entirely.
Psoriasis treatment, on the other hand, must address the overactive immune system and the resulting inflammation within the body. For milder cases, topical treatments like corticosteroid creams are used to reduce inflammation and suppress the localized immune response in the skin. More extensive cases may require systemic treatments, such as phototherapy, which uses ultraviolet light to suppress the immune cells in the skin, or biologics. Biologic medications specifically target key inflammatory messengers, such as tumor necrosis factor-alpha (TNF-α) or interleukins 17 and 23, to interrupt the internal immune cascade. Applying an antifungal cream to a psoriasis plaque will not resolve the problem because it fails to address the root cause.