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Is there any discharge present in the eye?
Is there any itching present?
Is the vision affected or not?
Is there any pain?
Blister may have been due to allergy. It is more likely to be an allergic conjunctivitis. Using an anti-allergic drop like Pataday 2 times a day should be helpful. The other possibility is that of viral conjunctivitis which will take it's own time(about a week). I would recommend that you use Pataday drops and if that does not help then see an ophthalmologist. Thanks and best wishes.
Pataday is not avalable OTC. You can go for Opcon-A. It is available OTC. Even claritin or benadryl will help but can cause drowsiness. The transient blister was most likely due to allergy and it's a good sign that it has gone. Swelling involving the lids could be both due to allergy or viral conjunctivitis. In viral conjunctivitis the eye is likely to be diffusely red. Seeing an ophthalmologist or optometrist will confirm the diagnosis. Thanks.