As an eye doctor, diagnosing a red eye can be challenging. Are we dealing with an infection, allergy, inflammation or dryness?

One of the most common questions I get is, “Doc, my eyes are red, burning, itchy, and tearing. Is this dry eye or from allergies?” The short answer is it could be one, both, or neither. I’ll outline various ways these conditions present clinically and the treatments for them.

The hallmark symptom of allergy – meaning if you have this symptom you almost definitely have the condition – is itching. Red, watery, ITCHY eyes are almost invariably due to an allergen, whether environmental or medicinal. It is one of the most common ocular conditions we, as eye doctors, treat -- especially when plants are filling the air with pollen as they bloom in the Spring and then die off in the Fall.

The itching occurs because an immune cell called a mast cell releases histamine, causing the itching sensation. It can be quite unbearable for the sufferer, causing them...

Demodex  folliculorum -- often just called demodex -- is a mite that occurs naturally on many people's faces and resides in hair follicles, particularly the follicles of eyelashes. Most of the time, these mites cause no problems whatsoever. However, sometimes an infestation can become particularly parasitic, resulting in unhealthy eyelid margins and leading to problems.  Those problems as a group are called blepharitis.  Blepharitis can be caused by caused by several things, including allergies, bacterial overgrowth, Rosacea and also by demodex.

Often, diagnosis of mite infestation by your eye doctor can be difficult.  The symptoms can mimic other causes of blepharitis, which is one of the most prevalent diseases we see.

The most common sign of a demodex infestation is a cylindrical cuff or "sleeve" at the base of the eyelash. Symptoms include redness, itching, burning, dry eyes and general discomfort in the eyelid.

The probability of demodex infestation increases...