Because of Allan's end-of-year performances, he was called up to the national team. Allan played a total of eight games in the Top 14 and four in the Heineken Cup in his debut season for Perpignan, scoring a total of 27 points in 12 appearances for the side. Perpignan were relegated to the Pro D2 after finishing 13th out of the 14 teams.
In the 2014–15 Pro D2 season, Allan cemented a firm position on the number 10 role for Perpignan. Playing eighteen games, scoring three tries, fourteen penalty goals, scoring a total of 81 points and helping Perpignan to reach promotional play-offs.
It was announced on 5 May 2021, that Allan had been signed by the English Premiership team Harlequins, to begin his career with them ahead of the 2021/22 season.[3]
International career
On 9 October 2013 Allan was named in the Italian 35-man training squad for the 2013 end-of-year rugby union tests,[8] which led to the Scottish Rugby Union seeking clarity on Allan's intentions for his future.[9] Despite Allan playing for Scotland at Under 17, Under 18 and Under 20 age groups, he was named in Jacques Brunel's final squad.[10] He made his debut coming off the bench to score against Australia.
Allan hails from a rugby family; his Scottish father William Allan and his Italian mother Paola Berlato both played in Italy, while his uncle John Allan earned 9 caps for Scotland and 13 for South Africa.[16] Through his father he was eligible to represent Scotland, but chose to play for Italy at senior level. He went to the European School in Culham, then graduated in economy in London to eventually get a master in marketing and business in Italy.