My friend visited a doctor about this effect. The doctor told him the geek method may have some serious side effects. Such as: Eye infection of many sorts (such as: uansiuasdu asidhaishd asjdhashd -I forgot the names sorry- excessive & unnecessary rubbing of the eye after the trick, and infections that will take a vast amount of time to heal). The doctor also said as much as you want to sanitize the string, it will have vast amounts of bacteria, and may cause harm to the body if it is left in the eye too long. As long as you follow instructions carefully every time, you will be safe.
Hope this helps,
Eugene