Lumps under the armpit could be swollen lymph nodes, which can indicate a weakened immune system. Your immune system may need some support, so I suggest that you speak with your doctor about options and make sure that the vitamins and supplements you are taking are helping your body, not hurting your body.

An abscess is caused by an acute infection of a small gland just inside the anus, when bacteria or foreign matter enters the tissue through the gland. Certain conditions - colitis or other inflammation of the intestine, for example - can sometimes make these infections more likely.

Thanks for your reply, the lump has since disappeared. Can doxycycline cause inflamation of the intestine as it apparently "prevents good and bad bacteria from forming".I m using it to treat acne i ve had for years.