Hi, Thanks for posting in HCM. I understand your concern. Naphcon Ophthalmic Solution contains Naphazoline , which is a sympathomimetic (alpha receptor agonist) that works in the eye to decrease congestion. It can be used as a decongestant to relieve redness, puffiness and itchy/watering eyes. Zaditor Ophthalmic Solution contains Ketotifen , which is an antihistamine and is used for the treatment of allergic symptoms, as it acts by blocking the formation of histamine. It is also a mast cell stabilizer that prevents allergic reactions by reducing the release of natural substances that cause an allergic reaction. Hence, this medication is used to prevent and treat itching of the eyes caused by allergies (allergic/seasonal conjunctivitis). Based on your condition and requirement, you can use any one of them, which would give you better relief. If allergy is your primary symptom, you need to use Zaditor. If allergic symptoms are associated with congestion of the eye, then you need to use Naphcon. Kindly do not mix the drops. Hope the information provided would be helpful. All the best.