From Quince website where I purchased: This shirt is the epitome of low-maintenance luxe. As a button-up, it's a classic wardrobe essential, but we love to wear it open as a spring/summer light layer. Our linen is made from 100% European flax, which is more sustainable and less resource-intensive to grow. Linen is the ultimate year-round fabric because it's breathable and naturally heat-regulating. DETAILS Ethically woven from 100% European flax linen Breathable, durable, hypoallergenic, lightweight This material is certified by OEKO-TEX Standard 100 (Certificate Number: BJ015 226317) which ensures that no hazardous substances are present