No optical brightener has been used. Non-chlorine bleach. By using only renewable materials in this product, we avoid using fossil or finite materials. We want to have a positive impact on the planet. That is why by 2030, we want all materials in our products to be recycled or renewable, and sourced in responsible ways. The cotton in this product is grown with less water, less chemical fertilizers and less chemical pesticides, while increasing profit margins for the farmers. That way, we lower our environmental impact.