Constant redness and watering are common symptoms often caused by dry eyes, allergies, or a mild infection. To safely soothe your eye, you can start by using generic, preservative-free artificial tears. If allergies are the cause, over-the-counter generic antihistamine drops (such as ketotifen) may help. Please avoid 'redness-relief' drops, as they can worsen symptoms over time. Because your eye is persistently dark red, it is best to avoid self-medicating with stronger drops. I highly recommend having an eye doctor examine your eye to provide an accurate diagnosis and prescribe targeted treatment, like antibiotic or anti-inflammatory drops, if necessary.