PM2.5 is a major air pollutant that can harm the skin by carrying toxic chemicals that penetrate through hair follicles. These pollutants activate certain receptors in skin cells, leading to changes in gene expression. The skin’s outer layer normally acts as a barrier, but when weakened, it increases the risk of allergies and conditions like atopic dermatitis (AD). A key skin protein, filaggrin (FLG), helps keep the skin hydrated and strong, but PM2.5 exposure can reduce FLG levels, leading to skin damage. While most research on PM2.5 focuses on lung and heart health, this study looks at how it affects the skin, showing that PM2.5 triggers inflammation (TNF-α), weakens FLG, and disrupts the skin barrier.