The 34-year-old played extra time for LA Galaxy for the second time in two weeks on Sunday and was coughing badly after the game.
‘David has suffered with this since he was a young boy, but it has obviously had no effect on his performance,’ his agent Simon Oliveira told the Daily Mail.
‘He has never sought to make it public but if it does inspire any sufferer to think they can achieve great things like many other sportsmen have done then so much the better.’
More than five million people in the UK are currently receiving treatment for asthma, a condition where the airways tighten and cause difficulties in breathing, according to Asthma UK.
‘Despite the fact it can be very serious for some people, if it’s well managed it needn’t stop you competing at the highest level as shown by David and other famous footballers like Paul Scholes and Frank Lampard, who both also suffer with the condition,’ the charity’s lead nurse Cher Piddock said.
‘Hopefully this news will inspire sport-loving children with asthma around the country and show that asthma doesn’t have to stop you achieving your dreams.’
Three-quarters of people with asthma say exercise is a trigger for the condition, Asthma UK said.
But if it is well-managed, taking part in sports activities can be beneficial because it improves lung function.
Marathon runner Paula Radcliffe, Olympic gold medallist Rebecca Adlington and cricketer Darren Gough are among the other high-profile sports stars whose asthma has not appeared to hold them back.
Beckham’s team lost the MLS final 5-4 on penalties to Real Salt Lake, although the Englishman scored his spot-kick.
But he had struggled with a cold during the build-up to the game and had pain-killing injections for a bruised right ankle before the match.
He was forced to limp through extra-time after the two sides were locked at 1-1 after 90 minutes and Galaxy had used their three substitutes.
Beckham will now turn his attention from the US to Europe when he rejoins AC Milan on loan next month.
He is hoping a run of games in Serie A will earn him a place in Fabio Capello’s England squad for the World Cup in South Africa next summer.