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What would cause unbearable painful bumps in armpit?
Swollen lymph nodes. You have lymph glands in your under arms, and they can become sore, sometimes you can even feel a knot, if your body is fighting on infection or illness. Not much you can do...
If they are little bumps, perhaps you have an allergy to the oils/scents used to massage you. Also the bumps could be white-heads caused by the oil clogging your pores.