The materials of the contacts might increase the likelihood for the eye infection and irritation. Moreover, the contact solution you used also might cause your infection and irritation. Once a doctor told me that some solution ingredients are not compatible with the materials of the contact lenses. Moreover, the contact lenses putting in the eyes just like foreign body resting on the surface of your eye ball. It is easy for your eyes get red.
So if you are experience a red eye and wear your contact lenses for a long time, you need to take it off and put on your frame eyeglasses. In this way, your eyes will be relaxed. Moreover, you also need to make sure that you are using the best contact solution for your lenses, in order to protect your eyes from infection and irritation.