The phenomenon of black underarms may be physiological reasons, there may be pathological reasons, such as acanthosis nigricans, dermatophytosis, etc., which should be based on different causes of different ways to make the underarms white, such as physical, pharmaceutical and so on. 1. Physiological reasons: part of the population due to personal hygiene unclean or women due to estrogen changes in the body during pregnancy and the phenomenon of black armpits, which is a normal physiological phenomenon, which can be cleaned or locally applied topical hydroquinone cream milk to make the armpits white. 2. Pathologic causes: (1) black acanthosis: it is a rare skin disease characterized by hyperkeratosis, hyperpigmentation and papillomatous hyperplasia of the skin, and it may also may appear the phenomenon of black underarms, and it can be whitened by oral or topical application of vitamin A to make the underarms. (2) dermatophytosis: due to dermatophyte infection and cause the body to appear a kind of infectious dermatosis, can appear erythema, blisters, peeling and hyperpigmentation manifestation, can lead to the body to appear the phenomenon of armpit black, which can be used to alleviate the symptoms of the external use of clotrimazole, miconazole nitrate cream and other drugs. If you encounter the above problems and have any questions, it is recommended to consult with a professional doctor and use the medication under the guidance of the physician.