Desensitization?! Tmi..

Soo I was cleaning our bathroom and found a scrub glove that had something hard in it so of course I checked inside and I find something called stud 100 genital desensitizer. I now know why my mouth goes numb occasionally when we have intercourse but my question is why does he already have this on before we even decide to? He has never told me about it. Some nights when he comes home from work my mouth will go numb if you know..so why is he only using this then?