What Does Swelling In Legs During Menstruation Suggest?

For the last 3 menstrual cycles, my legs swell from the knee down. I thought I had a food allergy because I was on vacation the first time it happened in March. However, it happened again a month later in April and now May. It seems to happen towards the end of my cycle and goes down with Benadryl. I took the Benadryl when I first thought it was a food allergy. The first two times this happened, I also developed red spots that were raised above the skin which also went away with Benadryl. I went to an urgent care facility and was told to take zyrtec for 5 days. The Doctor there didn t find anything alarming in my symptoms. Now it has happened again, this time with no red spots. There s no pain other than discomfort and tightness in my legs and feet. It causes me to gain about 10-15 pounds when this happens.