Henry Flescher was born in Vienna and escaped to France during WWII, only to be captured while trying to buy grapes at a market in Lyon.
He was sent to seven different German concentration camps over three years.
Mr Flescher, who did not know what Reddit was before his AMA, said his grandson helped him through the session, which received more than 7,000 questions.
“I hope this gives everyone a little perspective on life,” he said.
Mr Flescher still has a tattoo on his arm with his camp serial number 177153, used for identification at Auschwitz — the only camp where prisoners were tattooed.
When asked about the tattoo, Mr Flescher said he chose not to have the tattoo removed like other Holocaust survivors, as it would be like “removing a part of history”.
“It’s a testament to the past. It shows I survived. And I’m here, and loving life!” he said.
Mr Flescher narrowly avoided being sent to death at Auschwitz by sheer luck.
At 18, he was one of many being transported on a cattle car packed with prisoners with no food, water and just one bucket to use as a toilet.
“The smell was unfathomable,” Mr Flescher said.
After six days on the train, the guards selected 300 men. Mr Flescher was number 298.
Those 300 men were taken off the train while the others continued to Auschwitz where they were all killed.
“I will never forget the number 298.”
Day-to-day life in concentration camps
When plucked off the train, Mr Flescher said he was taken to work in a shoe factory at the Ohrdruf concentration camp for four weeks. He was then transferred to Peiskretscham where he helped build bridges.
“We worked 12 hours from six to six everyday,” he said.
After a few months there, he went on to Blechhammer, which he described as “hell”.
“Punishments were a daily routine and my front teeth were knocked out here,” he said.
“I still remember a friend of mine who was hanged because he was using a telephone wire as a belt to hold up his pants.”
Mr Flescher said when he went on to Gross Rosen, he once could not go to the bathroom for three days when he had dysentery.
“This was when I almost gave up,” he said.