Q: I know it wont give you diarrhea,as popular rumor has it,but is it possibly poisonous?
A: Let me present you some information from Snopes.com: Yet if Visine doesn't cause diarrhea, it has done things far more terrible. Drinking it can (and has) caused severe depression of the central nervous system. In 1996, a two-year-old child who ingested at most 2 to 3 mL of Visine eye drops became dangerously lethargic and unresponsive to every stimulus except deep pain. Thanks to prompt medical attention the child recovered, but not before enduring intubation and two days' worth of mechanically-assisted breathing. Medical literature reports other cases of small children brought to the brink of crisis by ingestion of tiny amounts of over-the-counter eye drops. The danger is real, and parents are well advised to keep eye drops away from children. Yet it is not only toddlers who risk central nervous system shutdown or other dire results if they swallow Visine. In 1995 an adult customer at a Whole Foods Market (a retail chain of natural and organic foods) had his wheat-grass smoothie spiked with a bottle of Visine by a clerk intent upon playing a practical joke. The victim, Rudy Trabanino of Houston, became violently ill and had to be hospitalized for several days with acute pain and a variety of serious medical problems. The clerk responsible for the act was dismissed, and Whole Foods Market settled out of court with Trabanino for an undisclosed sum after he brought a $1 million suit against the store. Visine poisoning has also featured in a murder. In 2001, Damien Kawai, a member of the U.S. Air Force, killed his roommate and fellow airman by strangling the young man, then attempted to conceal the crime by slitting the wrists of the corpse to make the death appear to be suicide. Kawai admitted to earlier spiking the roommate's beer with Visine, under the belief this would render the doomed man unconscious. (It actually caused him to vomit and suffer labored breathing). In May 2002, 19-year-old Damien Kawai was sentenced to life in prison for the 17 November 2001 murder of Charles Eskew. In October 2003, an unnamed Southern California high school student put eye drops in teacher's water bottle in an attempt to give his instructor severe diarrhea. Others in the class who saw the act removed the adulterated beverage before the intended victim could drink it. The student responsible has been charged with tampering with a drink with intent to cause harm. In June 2006, five Wisconsin high school students trying to pull the Visine prank poured about a quarter of a bottle of the eyedrops into a classmate's water. The victim spent several days in the hospital recovering from reactions to the poisoning that included a dangerously low heart rate and blood pressure. Each of the five "pranksters" pleaded no contest to misdemeanor counts of battery and disorderly conduct and received sentences of 18 months' probation and 60 hours of community service. Look at this URL: http://www.snopes.com/medical/myths/visine.asp