I think publicists use "drug reaction" as a generic cover. A while back someone posted about Bieber having a reported allergic reaction to drug hospital visit. Miley makes no illusions she parties with substances it's part of her public overcompensation against her Disney days.
She may have had a bad reaction to antibiotics. Medically that sort of puts her in the larger population allergic to some meds, not LTFA.
No hate on me for her transformation or whatever it was. I had no idea what she did before Bangerz but there's a couple of good tunes. She's got a real head for marketing for her age.
More for the interested reader.
Miley's gone on record as a vocal and ardent supporter of marriage equality and LGBT community support in general. I've watched/read her statements that people think she "looks gay" because of her hair cut and appearance and she's clearly said she doesn't care because gay is not an insult to her, nor should it be used as an insult. She's also helped publicize some Pride events. Thus far she's shown consistent support and fairly well thought out considering she grew up as a child star in Hollywood. The survival rate for child stars in Hollywood is not exactly overwhelming odds.
My on topic contribution. Our allergist is chomping at the bit to get DS1 on some tree nut challenges like he's just PSYCHED for it. Enthusiasm is good, I suppose.