Red eyes are usually a common symptom that resolves on its own within a few days. The most common causes are allergies or viral infections. However, if you experience red eyes along with the following symptoms, it could be a dangerous sign, and you should see an ophthalmologist immediately:

1. Blurry Vision: Red eyes accompanied by blurry vision often indicate a more severe eye problem
2. Severe Eye Pain: This may be a sign of a corneal abrasion, iritis, or acute glaucoma
3. Severe Light Sensitivity (Photophobia): This is often a symptom of iritis or a corneal abrasion
4. Seeing Halos or Rainbow-colored Lights Around Lights: This is often caused by acute glaucoma or corneal swelling