The Team Sky rider was granted TUEs in May 2013 and April 2014 to treat the condition but chose not to apply for a TUE - which allows athletes to take banned substances on medical grounds - when he was advised to do so during the 2015 Tour.
"I didn't feel having a TUE in the last week of the Tour was something I was prepared to do. It did not sit well morally with me," he told the BBC.
In 2013, Froome was allowed to use prednisolone for his asthma for a week before winning the Criterium du Dauphine while the following year he took it for a week during the Tour de Romandie, as he defended his title.
Bradley Wiggins and Team Sky have been under scrutiny since hacked medical records showed the Briton was granted TUEs for anti-inflammatory drug triamcinolone before the 2011 Tour de France, his 2012 Tour de France win and the 2013 Giro d'Italia.
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There is no suggestion that Wiggins, Froome or Team Sky broke any rules.
"I think WADA (the World Anti-Doping Agency) need to tighten their regulations around TUEs, so they're not something that we question, their legitimacy," added Froome.
"It's not good for sport in general. The fact that we're discussing the validity of results, that brings it back to the authorities, it is something they need to tighten up on so that there aren't questions being asked anymore."
(Reporting by Pritha Sarkar, editing by Peter Rutherford)
