The darkening of the outer corner of the eye area is usually caused by the following reasons: 1. It is triggered by eczema of the eyelid skin, which is commonly found in patients suffering from inverted eyelashes, inverted lids, tear duct obstruction, and chronic conjunctivitis. The above diseases will lead to increased tear secretion in the eye, or tear drainage is blocked, tears will flow from the outer corner of the eye. This will produce a soaking effect on the local skin, gradually causing the local skin to form a chronic allergic inflammation leading to eczema, and ultimately causing local skin pigmentation and blackening. 2, is due to the long-term use of prostaglandin derivatives eye drops, commonly found in patients with glaucoma, due to the need for long-term use of latanoprost eye drops, travoprost eye drops, bemeoprost eye drops and other prostaglandin Derivatives of the preparation, drug side effects lead to skin pigmentation around the eyes triggered by the blackness of the corners of the eyes. 3, is due to adrenocortical insufficiency, in the eyes of the characteristic performance caused. The disease will cause multiple skin pigmentation all over the body, to the corner of the eye area is the most obvious.