The singer was recently hospitalised in the US after what was described as "an allergic reaction" to a course of antibiotics prescribed by her doctor for a sinus infection.She was forced to cancel a number of US and European concert dates as a result of her illness.Speaking to journalists in the run up to her gig at London's O2 Arena on Tuesday, Cyrus said she was "the poster child for good health" ahead of her UK dates.The Wrecking Ball hitmaker, urged by a member of her entourage not to answer the journalist's "poor" question about what had happened to trigger the illness, dryly added: "But when people are lying on the internet saying you've had an overdose that makes you feel better."She said: "I'm feeling good, I'm alive, so that's f***ing awesome. Look at me, I'm the poster child for good health."I've been laying down for three weeks. I'm gonna go off - I'm like a star waiting to explode."I didn't have a drug overdose. I took some s****y antibiotic my doctor gave me and I had an allergic reaction."I already had a death in my family so my immune system was already low."Cyrus will continue her UK concerts in the coming weeks, including a date at Belfast's Odyssey Arena on Monday 19 May.