Taking care of one problem always seems to cause or exacerbate another! Antihistamines that help my coughing cause my eye to go red. Foot stretches that help my plantar fasciitis flare up the tendinitis in my knees. Lithium that helps my bipolar disorder causes kidney failure. Pretty much all OTC (and most prescription) meds to help my headaches or nausea can further damage my kidneys.
Life is too complicated.
So I'm stopping the Claritin as of today, and we'll see if the eye redness goes away.