If you do not want to let the sharpie ink get off your shirt, you need to be careful. You should not wash your shirt immediately and wait for at least 6 hours. You may use mild shampoo to wash it and never forget to iron it twice after washing. You should always prevent your shirt from dust, sweat and perfumes. However, sharpie pen with permanent ink options are also available in the market and it is always better to use a permanent marker.