Ears turning red sporadically can be caused by a rare condition known as red ear syndrome, according to a 2013 article in The Journal of Headache and Pain. The condition can also occur naturally depending on a variety of factors.
Red ear syndrome can cause your ears to turn red on their own or via a trigger like frequent touching of your ears or exposure to the elements. However, not very many people have this condition, so the more likely cause is blushing, explains WebMD. While blushing is typically caused as a result of being embarrassed, it is not always the reason why ears turn red. In some instances, blood can go directly into your ears and make them turn red if you go outside and are exposed to hot or cold elements.
If you are exercising heavily, your ears can also turn red as a result of increased blood flow. If you are anxious in a certain situation, your face and the surrounding areas may turn red, and that can cause your ears to turn red as well. Doctors on HealthTap indicate that allergies can sometimes trigger red ears. For example, if you are allergic to a certain type of food or medication, your ears might turn red and itchy or hot as your body's way of letting you know there is a problem.