BLOPENS are not messy but the spray can drift beyond the stencils. It is best to wear an apron, cover the work area, furniture and carpets with old newspaper. Stains on skin and most clothing can be removed with soap. Take breaks between using the pens to avoid continuous blowing. The mouthpieces are washable and interchangeable. Rinse out after use. They are completely safe for children to use with non-toxic ink.