just me ranting

someone please explain this to me

   I was just reading a fanfic and I had seen this particular thing happen in other books so I wanna know why.
   Y'all I'm 40 years old and I had never heard or experienced this thing so I am extremely confused and curious. It could be that I live in the south where its only cold all together about 3 maybe 4 months or it could be one of those things parents tell their children like if you swallow watermelon seeds you'll grow a watermelon in your stomach for the longest time I thought pregnant women had just swallowed a watermelon seed. Or its possible that with the amount I've seen it written it could be a real thing and if so what the hell kind of ice cream are y'all eating?
    Anyways the character eats ice cream more so than they should and in one book they experienced hypothermia but in most books where I've seen it the character gets a severe cold. I'm not a doctor but I have eaten a lot of ice cream and given my children ice cream I'm even looking forward to be the person that gives my grandbaby his first ice cream experience I've already promised him that when he learns to crawl I will get him some. The worst I've ever known someone to experience from eating ice cream is brain freeze and that only occurs if you eat it to fast.