Red and itchy eyes may be caused by infections such as adenovirus and herpes simplex virus, and may also be associated with pathogenic microorganisms such as Staphylococcus aureus and Chlamydia trachomatis. 1. Adenovirus: This virus infects the tissues of the eye and may cause viral conjunctivitis, in which the conjunctiva of the eye becomes congested and red, accompanied by an itching sensation. 2. Herpes simplex virus: This viral infection may cause viral keratitis, in which the patient may experience photophobia, tearing, redness of the eyes, and itching of the eyes. 3. Staphylococcus aureus: This bacterial infection may cause bacterial conjunctivitis, and due to the inflammation stimulation, patients may also experience symptoms such as eye redness and itchy discomfort. 4. Chlamydia trachomatis: This pathogenic microbial infection can induce trachoma, and patients may experience symptoms such as redness and swelling of the eyes, conjunctival congestion, and itchy eyes. There are many factors that can cause red and itchy eyes, so it is recommended to consult a doctor in time to find out the cause of the disease and carry out relevant treatment under the guidance of the doctor.