Contact lens related red eye 

 A contact lens can cause and eye to go red for many different reasons, for example infection, dry eye, mechanical injury

If you have a contact lens related red eye, remove the lens immediately, check it for rips and cracks, clean it and check it for obvious signs of deposits.  Failing this, do not wear your lenses until you have had a consultation with an optician 

If you have suffered a solution reaction, remove your lenses and irrigate the eye with water for at least 10 minutes