Don't know the cause, but, two tablespoons of plain yellow mustard will knock it out.

I can't help but think of Jesse Pinkman every time I see this thread title.

Have an epic case of mastitis which has left me with a fever between 100F and 103.3F for the past 30 hours or so. Aches, pains, etc. and trying to baby wrangle when all I want to do is nap. Thank God for Sesame Street on demand.