The Short:  AWFUL anal and vaginal itching stopped when I stopped my Progestin-only Camila birth control pills and also dairy.  They both, separately, cause me to itch. I’m off the pill, but dairy still makes me itch, and vice versa. 

The Long, in short, choppy sentences: Had colonoscopy. Slowly developed anal itching. Moved to vaginal itching as well, but never at the same time (neurological? Nerves misfiring in my brain?). Figured yeast infection that was all over that region. Saw doctor. Nope. No yeast. Sleep difficult, itching at night. Saw 3 more doctors — all tests (MANY) negative.  Tried everything for pruritus ani and all kinds of at-home remedies between doctor visits. Got prescribed a steroidal cream for the hell of it, really — the doctor was trying to help.  Desperation and determination led to online research and a string that listed 1.) food allergies and 2.) progestin birth control. THANK GOODNESS!  I get migraines with an aura (really, Complex Migraines) and I got a new birth control within the past few months due to having migraines with aura (birth controls with estrogen will ll increase your risk of stroke, which is already heightened by the migraines with aura, so I had to switch to progestin-only).  I guess my system couldn’t handle the hormonal changes what with my intestines losing their flora and fauna due to the colonoscopy (it takes years to properly repopulate).  I ALSO get itchiness due to dairy, since I am lactose-intolerant.  I had gotten off of dairy while still on the birth control and stopped it when I was still off of dairy. Lucky cioncidence. 

I have tested this by going off of the pill (felt better within hours), milk, both, and then re-introducing them one at a time, months later. Birth control can takes months to clear.