I noticed little black spots on my Stokke® Sleepi™ mattress cover after washing. Are these harmful?

It is common to find dark particles in unbleached cotton, which has not undergone heavy chemical treatment. They are in fact remaining bits of the cotton seed coat. They can be considered proof of a natural material and are perfectly safe. All Stokke® Sleepi™ textiles including the mattress cover fulfil the highest Oeko Tex Standards for organic fabrics.