Erythromycin eye ointment can promote mydriasis. Onychomycosis is often caused by staphylococcal infection, and erythromycin eye ointment belongs to the macrolide antibiotic eye ointment, which has a certain inhibitory effect on staphylococci and can confine the inflammation, which means it can promote the maturation of onychomycosis abscesses and manifest as yellow pus heads. Erythromycin ophthalmic ointment is a commonly used drug for the treatment of mydriasis. The main ingredients are erythromycin, liquid paraffin, lanolin and petroleum jelly. The widespread clinical use of this drug depends on its antibacterial effect on the one hand, and on the other hand, the lanolin, petrolatum, and liquid paraffin contained have lubricating and moisturizing as well as isolating effects. Clinical use of erythromycin ophthalmic ointment is occasionally associated with allergic reactions such as eye pain, vision changes, persistent redness or irritation, the incidence is low but should not be ignored. In case of allergy, the drug should be stopped immediately and cleaned up and replaced with levofloxacin eye drops for the treatment of mydriasis under the guidance of a physician, using hormonal eye ointment if necessary. The eye is often rubbed with dirty hands or the eye makeup is too heavy, so you should develop good hygiene habits, pay attention to eye hygiene, do not rub your eyes with dirty hands, eye discomfort can be wiped with a cotton swab dipped in saline to ensure clean eyelids. Try to wear light makeup on your eyes and pay attention to cleanliness before going to bed. Daily exercise, a light diet, avoiding excessive eye use, and timely treatment of eye diseases such as blepharitis can reduce the incidence of mydriasis.