Swelling and pain in the right eyelid of patients may be caused by mosquito bites, eye trauma, allergies, blepharitis, and so on. 1. Mosquito bites: When a patient’s right eyelid is bitten by a mosquito, due to the weak skin of the eye, under the stimulation of toxins, the right eyelid will easily appear to be swollen, painful and other symptoms, which can also be accompanied by itching and other discomforts of the eye. 2. Eye trauma: If the patient’s right eyelid is impacted or eroded by chemicals, it will easily lead to eyelid injury, and the patient may experience eyelid swelling, pain and other discomforts, which may also be accompanied by eye bleeding, vision loss and other discomforts. 3. Allergy: When the patient’s right eyelid comes into contact with allergic substances, such as dust mites, animal fur, etc., allergic reactions are easily induced, and the patient may experience discomfort such as swelling and pain in the right eyelid, which may also be accompanied by itching. 4. Blepharitis: Blepharitis refers to suppurative inflammation of the eyelid glands, which may be caused by patients not paying attention to eye hygiene or rubbing their eyes with their hands on a regular basis. Patients may experience redness and swelling of the eyelids, pain, and an increase in secretions. It is recommended that patients with significant redness and swelling of the eyelids should seek prompt medical attention to evaluate their condition and follow the doctor’s instructions for treatment.