Monocular ocular allergies causes?

Dust? Dust or another allergen could be introduced into one eye under unusual circumstances and cause symptoms in one eye. Make up introduced into one eye is also possible causing a contact reaction. Contact lens solution could be the culprit if you use a contact lens in one eye only. You may have infectious conjunctivitis and not allergic conjunctivitis. An antibiotic may be needed. See your md.