Environmental protection, not any poison, ink is nontoxic. Auto vanishing pen is best used by shoes industry, especially use in sport shoes for temporary marking. The writing will disappear spontaneously, the disappear time can adjust. We Passed U. S. ASTM F963-03 TOXIC ELEMENTS TEST; And EN71 PART 3: 1994 AND AMENDMENT A1: 2000 TEST. We have multi-design. WARNING Auto vanishing pen is the same with disappearing ink pen and air erasable pen in some condition. Use the auto vanishing pen in its available time. Please use "the water" or "clearning pen" to get rid of the writing, if the writing do not disappear on normal situation. the disappear time is limited to the material, air wet condition, temperature, and so on.