It really depends on each person's pain tolerance. I actually do not have that much hair there at all. First time I did it, it brought tears to my eyes. But now I barely feel it. The more you do it, the less pain you tend to feel.
Also you can numb the are before you do it.
Are you asking if it hurts to get your arm pits waxed? If so, yes, it does a bit. You are getting your hair ripped out of your skin...it's worse than pull a band-aid off...but the pain only lasts for a little bit.
how long does it last?