Redness can indeed be a symptom of an allergic reaction. An allergic reaction is triggered by the body when it encounters an allergen, like pollen or certain foods. In response, histamine is released, causing various symptoms, including redness of the skin or eyes. In the affected area, the dilation of blood vessels increases blood flow, resulting in redness. So, if you notice redness after coming into contact with a potential allergen, it's possible that an allergic reaction is to blame.