Psoriatic arthritis (PsA) is a chronic inflammatory disease affecting the joints, often in people who also have psoriasis. While PsA does not directly cause permanent hair loss, the underlying inflammation, associated skin disease, and necessary medical treatments frequently contribute to hair thinning and shedding. The causes of hair loss in PsA fall into three main categories: systemic inflammation, localized scalp damage, and pharmaceutical side effects. This hair loss is generally temporary and requires specific attention to manage effectively.
Systemic Inflammation and Hair Shedding
The chronic, body-wide inflammation characteristic of active PsA can indirectly trigger Telogen Effluvium (TE), a form of diffuse hair shedding. This temporary hair loss is a stress response where severe systemic disruption prematurely forces a large number of growing hair follicles into the resting phase. High levels of pro-inflammatory cytokines, such as TNF-α and IL-17, circulating during a PsA flare-up act as a physiological shock to the hair cycle.
Instead of gradual shedding, a significant percentage of hair follicles enter the telogen (resting) phase simultaneously, resulting in noticeable thinning across the entire scalp. This shedding typically occurs two to three months after the inflammatory event. Since TE is non-scarring, regrowth is expected once the systemic inflammation is brought under control.
Localized Hair Loss from Scalp Psoriasis
A more direct cause of hair loss is inflammation from psoriasis when it affects the scalp. Scalp psoriasis is common, affecting nearly half of all individuals with psoriasis, and creates thick, scaly patches. These plaques disrupt the stability of the hair shaft and surrounding tissue, weakening the hair’s anchor.
The primary mechanism for this hair loss, often called psoriatic alopecia, is mechanical damage and localized inflammation. Severe scaling adheres to the hair shaft, and forceful removal of these scales can inadvertently pull out attached hairs. Furthermore, the intense itchiness associated with the plaques often leads to scratching, causing trauma and breakage to the hair shaft and follicle. While this damage is typically temporary, severe, untreated scalp psoriasis can rarely lead to follicular destruction and permanent scarring alopecia.
Medication-Related Causes
Many medications used to treat PsA inflammation can cause hair loss, often representing the most significant cause of thinning. The conventional disease-modifying antirheumatic drug (DMARD) methotrexate is a common example, causing hair loss in 1% to 3% of users at the low doses prescribed for PsA. Methotrexate interferes with the metabolism of folate, a B-vitamin necessary for the rapid division of cells, including those in the hair follicle.
Another DMARD, leflunomide, affects up to 10% of patients. This drug also targets rapidly dividing cells, explaining the effect on hair growth. Hair loss from these medications is generally diffuse thinning that is dose-dependent and reversible upon dose reduction or discontinuation. Biologic agents, such as TNF inhibitors, are less commonly linked to hair loss, but they can sometimes trigger or worsen the skin condition, indirectly leading to shedding.
Management and Mitigation Strategies
Addressing hair loss requires a targeted approach based on the specific cause, beginning with a consultation with a rheumatologist or dermatologist. If Telogen Effluvium from systemic inflammation is suspected, the primary strategy is achieving better control of PsA, as reducing disease activity lowers the body’s overall stress. Patients must not stop or change medications without medical guidance, since uncontrolled PsA can lead to irreversible joint damage.
For localized hair loss due to scalp psoriasis, treatment focuses on clearing plaques and minimizing trauma. Medicated shampoos containing coal tar or salicylic acid can soften and loosen scales, reducing the need for forceful removal. Gentle hair care is paramount, including resisting the urge to scratch and avoiding harsh chemical treatments or excessive heat styling.
In cases of medication-induced hair loss, a doctor may adjust the dosage or switch treatments. For patients taking methotrexate, a routinely prescribed folic acid supplement can help mitigate hair thinning without compromising the drug’s effectiveness against PsA.