What Causes Swelling On The Face?

Hi, I am a 46 year old white female and have been experiencing a type of reaction that has me concerned. I had the first reaction about 2 years ago. When I was in the shower, I noticed that my face was getting hot and felt like it was swelling. When I got out and looked I saw that the redness was around my mouth, down my neck and shoulders and there was significant swelling around my mouth. It lasted about 20-30 minutes and subsided(I did take Benadryl). A couple of months later, the exact same thing happened even down to being in the shower when I felt it come on. Same duration but went away without even taking Benadryl. I had a few more reactions and decided that I thought it might be an allergy to mango so I have quit eating it completely(last consumed around a year ago). I have had no further reactions.....until today. I was at my desk working this morning and noticed the hot tingling sensation around my mouth. Within a few minutes, I was red and swollen around my mouth and redness continued down neck. I went and sat with one of the nurses that I work with and it shortly passed(about 15-20 min). I have not taken Benadryl with any of the reactions except the first one. I do not have any trouble breathing when they happen. Once they have ceased though, I feel really crummy after. Today I have felt very tired and had a terrible headache ever since(it actually reminds me of a hangover). Just curious if you can give me any clues on what in the world this could be. I also must note that I did not eat anything for supper or breakfast today that I have not eaten 100 times before. Thank you for any help you can offer. Sincerely, Rachael