Small red dots on the breasts in the 21st week of pregnancy may be caused by skin allergies or eczema. 1. Skin allergies, 21 weeks pregnant breasts long red dots may be due to improper clothing or contact with some kind of allergens caused by the allergic phenomenon, manifested in the skin around the breasts have small red dots, rashes, and itching discomfort symptoms. Under the guidance of a doctor, you can use local glycerine lotion to relieve itching, take calcium gluconate and other drugs to fight allergies, and wear cotton, good ventilation clothing to observe. 2. Eczema, women’s metabolism after pregnancy, easy to sweat, such as wearing bad ventilation underwear or too tight underwear, can lead to breast skin eczema, resulting in small red spots and itching and other symptoms. You can use glycerin lotion or eczema ointment and other medications under the guidance of a doctor, pay attention to changing underwear, do not wear tight underwear, and avoid eating stimulating foods. It is recommended that any discomfort during pregnancy, timely medical treatment, symptomatic treatment.