Sudden one eye pain and long eye boogers may be related to allergen stimulation, or it may be caused by granuloma, eye inflammation and other reasons. 1. Allergen stimulation: commonly found in people with allergic body, if one eye is subjected to allergic stimulation, such as after contact with cosmetics, shampoo and other substances, it is likely to cause allergic reactions, then it may suddenly have one eye pain, long eye droppings, and may be accompanied by itching, tearing and other symptoms. 2. Eyelid swelling: If one eye suffers from granuloma, it may cause a sudden eye pain, long eye boogers, and may be accompanied by eyelid congestion, swelling and other symptoms, mainly due to the eyelid edge of the eyelash follicle root of the blepharoplakia or sebaceous glands caused by infection. 3. Eye inflammation: It is common in conjunctivitis, keratitis and other diseases, because one eye suffers from conjunctivitis, keratitis, under the stimulation of inflammation, it may cause a sudden eye pain, long eye droppings, and may be accompanied by tearing, photophobia and other symptoms. Sudden pain in one eye and long eye droppings may also be caused by other reasons, it is recommended to consult a doctor as soon as possible to clarify the cause of the disease and then carry out targeted treatment.