Why do eyes become red during a summer cold?

When having a summer cold, red eyes may be caused by conjunctivitis due to a viral infection, commonly known as "pink eye." This may be due to the following reasons: 1. **Lack of sleep**: If symptoms such as nighttime coughing or fever accompany the cold, they may lead to insufficient sleep. Overuse of the eyes can cause congestion of the ocular capillaries and result in red eyes. 2. **Subconjunctival hemorrhage**: Symptoms such as nausea, vomiting, severe coughing, sneezing, and fever associated with the common cold may increase the tension of small blood vessels in the eyes, causing eye congestion and redness. In severe cases, it may even lead to rupture and bleeding of small conjunctival vessels. 3. **Eye inflammation**: During a cold, the mucous membranes of the upper respiratory tract may become infected with pathogenic microorganisms, triggering a series of inflammatory responses. These pathogens can cause eye inflammation, such as conjunctivitis, through the nasolacrimal duct or by touching the eyes with contaminated hands, leading to symptoms such as redness, pain, and increased eye discharge.