Why did nair burn me in less than 3 minutes??? & didnt even remove all the hair😑

I wanted to stop shaving bc it was causing such hyperpigmentation on my lady bits and underarms to the point where I had to use a toner on both bc I personally hate the way that looks, so my friend recommended trying Nair, said it was great & lasts longer & leaves skin smoother than shaving, i put in on my underarms first to try it out (thank God) , let it sit 2.5 minutes begin I felt burning..i rinsed it off & my underarm skin is completely burned off in the crease and all of the hair isnt even gone😑 WHY