Dark circles under the eyes are not exclusive to adults, many children start to have dark circles at a very young age. Most parents think that their children are not well rested, or that they are frightened, so what is the real reason? The following is an introduction: dark circles under the eyes are also called “allergicshiners” (there is no corresponding Chinese translation yet, meaning related to allergies). The most common cause of dark circles under the eyes is nasal congestion, and the most common cause of long-term nasal congestion is allergic rhinitis. The principle of dark circles under the eyes is: nasal congestion causes increased resistance to blood circulation around the nose, resulting in blood displacement and congestion in the face, and capillary congestion around the eyes, thus causing dark circles. When fluid is retained in the blood vessels, it flows into the tissues and causes swelling of the lower eyelids. Dark circles under the eyes can become more pronounced with exposure to allergens. Some children have dark circles only seasonally, while others have them all year round. A common allergen is the one that causes allergic rhinitis. Outdoor allergens are more often considered for seasonal aggravation, and indoor allergens are more often considered for those who have them all year round. To alleviate the dark circles under the eyes you should pay attention to avoid allergen exposure. Usually, you should pay more attention to cleaning the nasal cavity, using sea salt water or physiological saline, which can help relieve the blockage and reduce the dark circles under the eyes. If nasal congestion or coughing is obvious, seek medical attention. The doctor may prescribe hormonal nasal sprays and oral anti-allergy medication.