Mother in law has blood shot eye in the corner started 3 days ago and getting bigger ... no known reason ?

?Scleritis: Ok, sometimes, even the pressure of a sneeze or hard stifled cough can rupture blood vessels in the whites of the eye. If no symptoms, that what it might be, and time will heal that. If red, inflamed, itchy, getting worse, draining,..it may be a "pink eye" or Conjunctivitis which is contagious and she should see the Dr. Best wishes to your M-I-L.

Could be: A simple as ruptured blood vessel causing a "bruise" in the eye - a so called subconjunctival hemorrhage. But it could be a sign of some sort of inflammation. Your mother in-law should seek help from her doctor, particularly if she has pain or any changes in the quality of her vision. Best of luck

If not better, exam: If your eye otherwise feels relatively normal but looks terribly "tomato ketchup" red, you likely have a subconjunctival hemorrhage. Usually these are a result of mechanical (rubbing) mechanism but some are from sneezing, coughing, & straining. If you take Aspirin or other anticoagulants, they are more common. Artificial tears are adequate for soothing. If itchy eye component, then try Zaditor™