Over the past few months I've noticed an occasional bump on my left arm, on the underside, about midway between the elbow and the armpit. It's like a mosquito bite, but larger, and mildly itchy. I usually treat it with aloe. I've noticed it three times, and every time it seems to grow and fade away in... perhaps an hour, maybe longer. It wouldn't unnerve me, except it seems to be happening in about the same place every time. Can anyone help?