Hi, Thanks for posting in HCM. I understand your concern. Swelling of labia during menstruation could be due to local allergic reaction due to use of tampon or pads. Kindly wash the area thoroughly with cold water and mild antiseptic solution like Savlon twice daily. Apply Hydrocortisone cream over the lesion after drying. Kindly take antihistamine medication like Levocetrizine once a day and antiinflammatory medication like Ibuprofen after food. You need to change the brand of pad or tampon you are using to overcome such reactions in future. Hope the information provided would be helpful. All the best.