Medical Conditions/ Diseases
Dark circles under your eyes can be as a result of underlying medical conditions. For example, during an allergic reaction to allergens, the body releases histamines which not only lead to reddening of skin and itchiness but also cause the dilation of blood vessels. The dilation of blood vessels under your eyelids causes dark circles. Other medical conditions that contribute to the formation of dark circles include insomnia, malnutrition, asthma, contact dermatitis, eczema, anemia, liver disease, and dehydration.
With age, your skin starts to thin due to the loss of fat and collagen. This makes the underlying blood vessels more conspicuous appearing as dark circles.
Too much exposure to the sun, especially to your eyes, leads to excess melanin production. This causes pigmentation in the skin underneath your eyelids, leading to the formation of dark circles.
Pigments irregularities mostly occur in dark-skinned people. The skin under the eyes undergoes hyperpigmentation or excessive melanin production, causing dark circles.
Apart from oversleeping and insomnia, other lifestyle factors can lead to the darkening of the skin surrounding your eyes. These include stress, medication, alcohol, and smoking.