I've had this since a child and now early 50s. My mother (mid 70s) has it and so does my teenage son. Entering and leaving different temperatures sets me off. I'm not quite so bad in the summer as indoors and outdoors tend to be similar temperatures. I remember as an older teenager being asked if I was ok as people thought I was crying. I'm a supply teacher now and sometimes a child in a class will ask me if I'm crying (usually the little angels who would drive any normal person to drink). I have a constant supply of tissues with me at all times.
I'm not allergic to anything that I know of but have developed psoriasis and another auto immune condition in the last few years.
Anyone else suffer from this?