Disease Overview:The lesions are light brown or yellow-brown spots with clear borders and irregular shapes, symmetrically distributed near the orbits, forehead, eyebrow arch, nose, cheeks, lips and perioral area, without conscious symptoms or general discomfort. Etiology】 The etiology is unclear, and is often thought to be related to endocrine function changes. It is often thought to be related to endocrine function changes. It is seen in women who are pregnant or taking oral contraceptives and other factors. Chloasma gravidarum (pregnancy chloasma) starts in the third to fifth month of pregnancy, and the pigmentation gradually disappears after delivery. Facial hyperpigmentation may be due to the combined action of estrogen and progesterone, which stimulates melanocytes, and progesterone, which promotes the transit and diffusion of melanosomes and increases melanin production prompting hyperpigmentation. It is also seen in chronic gastrointestinal disease, liver disease, tuberculosis, cancer, malignant lymphoma and chronic alcoholism. Long-term application of certain drugs such as sodium phenytoin, dormant, and birth control pills can cause chloasma. In addition, strong sunlight and cosmetic application can also induce chloasma. Chloasma is also seen in unmarried, non-pregnant normal women or men, and its cause is unknown. [Pathological changes] There is excessive pigmentation in the epidermis and more pigment in the dermis with phagocytic melanocytes. There is a small infiltration of lymphocytes around the dermal blood vessels and hair follicles. Clinical manifestations The lesions are light brown or yellow-brown spots with clear borders and irregular shapes, symmetrically distributed near the orbits, forehead, eyebrow arch, nose, cheeks, lips and perioral area, without conscious symptoms and general discomfort. The lesions are light brown or yellow-brown spots with clear borders and irregular shapes, symmetrically distributed near the orbits, forehead, eyebrow arches, nose, cheeks, lips and around the mouth, without conscious symptoms and general discomfort. Treatment and prevention Avoid sun exposure, and try to remove the cause of the disease if there is one. Melasma caused by birth control pills should be stopped, but it may not necessarily subside in a short period of time. 1.Systemic treatment Take large amount of vitamin C orally, 1~3g per day, or vitamin C 2g by injection. Vitamin C can reduce the darker oxidized pigment to lighter reduced pigment and reduce dopaquinone to dopa, thus inhibiting the formation of melanin. 2.Topical treatment Topical topical application in combination with oral medication is more effective. (1) Depigmentation agents 1) hydroquinone preparations 3% to 5% hydroquinone cream, 2.6 tert-butyl p-phenol cream, 10% to 20% hydroquinone monophenylether cream and 3% hydroquinone monopropionate, topical application can be effective. Hydroquinone mainly blocks the reaction process from tyrosine to dopa catalyzed by tyrosinase to reduce melanin formation, that is, it prevents the oxidation of tyrosine to dihydroxyphenylalanine (do-pa) and effectively prevents melanin production. Hydroquinone cream should not be applied to the normal skin near the damage, and should not be used too much to avoid patchy and uneven skin color. Very few patients can be allergic and dermatitis can occur. 20% monobenzyl ether of hydioquinone emulsion or ointment can be applied to turn hydroquinone into hydroquinone in the skin to play the same role, it may be effective for stubborn cases, attention should be paid to easy to cause allergy and uneven depigmentation or permanent depigmentation. (2) Retinoic acid preparation Use 0.1% retinoic acid, 5% hydroquinone, 0.1% dexamethasone into hydrophilic ointment or into an equal amount of propylene glycol alcohol solution (the solution must be freshly prepared). It can be applied topically 2 times a day, and there is often erythema irritation at the beginning of treatment, and the pigmentation can be significantly reduced after about 4-6 weeks. (3) 2-5% hydrogen peroxide external rubbing can also be decolorized. (2) Shading agent In the treatment of melasma, shading agent is used to enhance the therapeutic effect. Shading agents can defend against ultraviolet light and visible light, thus protecting the skin from damage and preventing pigmentation. (1) Para-aminobenzoic acid (PABA) absorbs medium-wave ultraviolet light (280-320nm) easily. The 50% to 60% alcohol solution of 5% PABA is the most effective, note that it can cause allergy. It is currently used clinically. (2) Phenyl salicylate (also known as Salo, Salol) is often formulated into 10% cream for external use. (3) titanium dioxide 5% titanium dioxide cream for external use, with the role of sun spots. (3) anti-skin aging agents 1) 1% vitamin E cream topical vitamin E can inhibit free radical-induced lipid peroxidation and prevent skin aging