Blepharitis is not contagious. Blepharitis is an acute purulent inflammation of the glands of the eyelids, including inflammation of the lid glands, eyelash follicles or accessory glands. Most are caused by staphylococcal infections, particularly Staphylococcus aureus. Internal mydriasis inflammation is confined to the lid gland and presents as a congested, swollen, painful eyelid with limited congestion and edema on the conjunctival surface of the lid, and after 2-3 days, a yellow pus spot forms. In external mydriasis inflammation at the lid margin at the base of the eyelashes, the eyelid will be locally congested, swollen, and painful, and hard nodules may be palpable. When the lesion is located in the external canthus, bulbar conjunctival edema may occur, and after 2-3 days, pus spots form at the root of the eyelashes, which may break down and drain pus on their own. In severe cases, the face on the same side is swollen, the preauricular or lymph nodes are enlarged, and even cause systemic toxic symptoms such as fever, headache, nausea and vomiting.