The Swansea-born 20-year-old centre, who played for Wales Under-20s last year but has a Scottish mother, played well for Irish in their 21-19 Premiership win over Sale Sharks in Reading on Sunday.
And that was "credit to him", said Booth, after a week where his international future was called into question.
The International Rugby Board have been contacted about the situation by both the Scottish and Welsh Rugby Unions.
Wales claim his appearance for the Under-20s makes it impossible for Scotland to select him, while the Scots say Shingler has "declined to sign a document declaring himself to Wales".
All this happened while Shingler was preparing with Irish for this weekend's game, where he was due to be on the bench but eventually started when England ace Shontayne Hape suffered a late injury.
Booth explained why the club were shielding Shingler from explaining the situation, saying: "When it all broke and there were some questions over it, it affected him quite badly.
"As far as we are aware - and there is some stuff around from his agent - Steve Shingler is qualified for Scotland and will be taking up that unless he is advised or informed by the IRB not to do so.
"It is a massive distraction along with, by his own admittance, an ordinary performance (against Bath) the week before.
"So he was back in his more familiar position today and played well. But I'm sure people will understand the situation we are in.
"His agent and him are taking legal advice about the whole situation and I've just told Steve to concentrate on what he does week in and week out."
Booth added: "I am not up to speed on non-English qualification. As far as I was aware, it was always Sevens, A team, Saxons and full international (sides) and I'm unaware of anything that is different to that."
The Irish head coach heard about it from the player himself after the Scottish Rugby Union named him in their Six Nations squad.
Booth added: "Steve Shingler phoned me up - and all credit to him as an individual - to ask my advice on the situation as in pledging to Scotland and he wants to play international rugby.
"He has the privilege of being eligible to play for three countries (England, Wales and Scotland) but like any player, all he wants to do is play international rugby.
"His biggest concern was that it was not going to affect his long-term future at London Irish if he became Scottish. That says a lot about Steve Shingler. I don't want him hung out to dry - I just want him to play rugby."
The SRU said: "Steven has informed us that he made it clear that he wished to leave open his international eligibility as he was also eligible to represent Scotland and England as well as Wales."
However, as Wales do not run an A team - equivalent to England Saxons, for example - at international level, which would mean anyone playing in that side could not play for another country, their Under-20s could be considered as their second XV squad
Wales claim this means Shingler can only represent them in the future.
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