Azelaic acid gel tolerance can generally be established by concentration, by area, by duration, and by frequency. 1. By concentration: the gel can be mixed with the lotion proportionally to achieve the purpose of diluting the concentration of the gel, so as to reduce the irritation of the gel on the skin, and then slowly increase the proportion of the gel, and finally can be used directly. 2. According to the area: you can first apply the gel to the affected area, and then slowly expand the area, until the whole face to use. 3. According to the length of time: the gel will be applied to the affected area of the skin for 3 to 5 minutes and then cleaned up, observe whether the skin has redness and stinging, and then let the gel stay on the face for a few minutes more when you use it again, and then slowly increase the length of time to overnight. 4. According to the frequency: you can first use 1 to 2 times a week, then become every other day use, and finally daily use. Azelaic acid gel clinically used in the treatment of mild and moderate acne; in the use of the main is applied externally to the acne localization, pay attention not to contact with the eyes, lips and mucous membranes and other skin sensitive places; common adverse counter-symptoms are redness and stinging of the skin, itching, etc., at this time the need to immediately stop the drug; allergic to azelaic acid, can not be used. If the condition requires the use of azelaic acid, it is recommended to use under the guidance of a professional doctor.