Gunners coach Mikel Arteta hopes the illness is not serious as Arsenal have suffered a number of injury and illness problems so far this season. North Londoners are last in the Premier League after three games.
U21 manager Lee Carsley has confirmed the incident is not related to coronavirus after the Young Lions saw a friendly in Romania canceled following an outbreak at their camp.
Carsley has been preparing his team for their first game in charge against Kosovo on Tuesday night, but lost a key man in Smith Rowe.
“It is not related to Covid,” Carsley told Sky Sports. “He just felt bad, so we decided to send him back to Arsenal.
“He wasn’t feeling 100 percent, so the best thing he could do for Emile was send him back.”
Cole Palmer replaced Smith Rowe in the starting eleven with another Arsenal man in Folarin Balogun named on the bench.
There will be concerns in North London now that Arteta will not be able to call in Smith Rowe, who recently signed a new contract, in his Premier League match against Norwich.