A TikTok user's viral video has revealed the surprising connection between dark circles under the eyes and allergies. Many people associate these dark circles with lack of sleep, but they can also be a sign of underlying health issues. This discovery by the user's dermatologist shows that these circles, also known as allergic shiners, can be caused by congestion in the nose and sinuses, and are often found in people with allergies. The video has sparked conversation about the link between allergies and dark circles, shedding light on a commonly overlooked symptom.