Psoriasis vulgaris (PsV) is influenced by genetic, epigenetic, and environmental factors, with seasonality playing a key role in disease activity. Seasonal factors like sun exposure, humidity, air pollution, and circadian rhythms can impact severity by altering gene expression linked to the immune system’s proinflammatory responses. Disturbances in circadian rhythms, such as changes in sleep patterns or shift work, can also worsen symptoms. Patients are more likely to experience flare-ups during winter due to reduced sunlight, higher air pollution, and lower humidity, while warmer months may provide some relief, though not for all.

Emerging evidence suggests that the timing of therapy initiation may affect treatment outcomes, with better results for those starting treatment in warmer months. While sunlight exposure benefits many patients, excessive UV exposure can trigger photosensitive psoriasis (P-PsV) in some. The role of vitamin D in PsV remains unclear. Cultural and regional factors also influence psoriasis severity, with different seasonal patterns observed in various geographic locations. Further research on seasonality and psoriasis is needed to improve treatment strategies and healthcare planning.

Reference: Niedźwiedź M, Skibińska M, Ciążyńska M, et al. Psoriasis and Seasonality: Exploring the Genetic and Epigenetic Interactions. Int J Mol Sci. 2024 Oct 30;25(21):11670. doi: 10.3390/ijms252111670. PMID: 39519223; PMCID: PMC11547062.