Swelling of labia majora may be related to inappropriate sex life, or it may be caused by allergic reaction, vulvodynia and so on. 1. Improper sex life: for example, frequent sex within a short period of time, or excessive force during sex, resulting in localized blood vessel rupture, etc., may cause swelling of labia majora. 2. Allergic reaction: Commonly found in people with allergic body, such as allergic to the material of underwear, allergic to sanitary napkins, etc., which may cause swelling of labia majora, and may be accompanied by obvious itching, pain and other symptoms. 3. Vulvovaginitis: usually caused by poor personal hygiene habits, overactive sex life, or excessive washing of the vulva, due to the presence of inflammatory reactions in the vulva area, the stimulation of inflammatory products may lead to the swelling of the labia majora, which may be accompanied by localized itching, burning pain and other symptoms. Swelling of the labia majora may also be caused by other reasons, it is recommended to consult a doctor as soon as possible, after clarifying the causes, to give targeted treatment and adjustment.