Omeprazole has various side effects and some can be very serious like bloody stools, difficulty in breathing, skin rashes and more. To prevent side effects from happening in your body always use omeprazole as directed by your doctors and do not take it for long durations like 1 year or so. For more about omeprazole side effects visit http://myotcworld.blogspot.in/2012/06/how-serious-are-omeprazole-side-effects.html