The Cardiff Blues centre has been named in a 24-man training squad and will link up with Team GB today.
Allen spent much of the second half of the season side-lined due to an ankle injury but he is returning to fitness and will travel with the squad for the Moscow Sevens.
He never thought he would have the chance to take part in the multi-sport event but he does not want to let it slip through his grasps.
I spoke to Gareth Williams (Wales Sevens coach) and he asked if I would be interested, then a couple of weeks later I had a call off Simon Amor (GB Sevens head coach).
“I said if my name was in the mix I would definitely be keen. I spoke to Warren Gatland and Rob Howley, I spoke to Danny and they were good as gold.
“It’s a massive honour, to be in and around the GB squad for the Olympics, it doesn’t get any better. Now I have to knuckle down and try to get in that final squad.
“Playing rugby the Olympics doesn’t come into your mind but when it was announced that it would be introduces, it was something I would be keen to do if the opportunity came about.
“It would be incredible to go but the hard work starts now.”
Allen will train with the squad in London ahead of the Moscow Sevens and then embark of a three week training camp.
Team GB will then feature in two more sevens tournament before head coach Simon Amor whittles the squad down to a final 12 for Rio 2016.