Repeated sudden swelling of one eye can happen due to allergy, eyelid gland blockage, recurrent infection, insect bite reaction, sinus-related inflammation, dry eye irritation, or swelling of tissues around the eye. Since you were given Doxycycline, Ecotear, and Incid-L, the doctors may have been considering inflammation, infection, dryness, or allergic causes. Temporary improvement followed by recurrence suggests the underlying trigger may still not be fully identified. The exact pattern of swelling matters. Allergy-related swelling often appears suddenly with itching or watering, while gland blockage or eyelid infection may cause pain, heaviness, tenderness, or localised swelling near the eyelid margin. Dry eyes and excessive eye rubbing can also irritate the surrounding tissues repeatedly. Cold compresses, avoiding rubbing the eye, maintaining eye hygiene, and limiting exposure to dust, smoke, cosmetics, or strong allergens may help reduce flare-ups. If swelling is associated with fever, vision changes, severe redness, pain while moving the eye, or facial swelling, further evaluation may be necessary to rule out serious infection or inflammation.