Allergic conjunctivitis can cause swollen eyes, mainly due to acute allergic conjunctivitis, contact allergic conjunctivitis, or seasonal allergic conjunctivitis, which is caused by itching and rubbing of the eyes. If it is accompanied by severe congestion of the white of the eye and edema of the conjunctiva, it is necessary to use anti-allergy medication, such as Flomipron or Dimethoate, which contain hormones and are relatively strong and can suppress the allergy in a short period of time, so that the itchiness of the eye will be reduced and the edema and redness will gradually subside after not rubbing the eye. Allergic conjunctivitis can cause eye swelling, but the swelling is usually not painful and is mainly itchy and foreign body sensation.