LONDON • Bradley Wiggins is facing mounting pressure to justify his use of allergy medication after the British cyclist, and Team Sky, came under fresh controversy over their use of injections on Sunday.

Wiggins issued a second statement over the weekend about the three triamcinolone acetonide jabs that he received shortly before grand tour races, including his 2012 Tour de France victory.

Triamcinolone acetonide is a banned substance but Wiggins was given permission, through therapeutic use exemptions (TUEs), because of a severe pollen allergy.

But one leading sports scientist within cycling said that Team Sky's image for being "squeaky clean, cleaner than the rest" had been called into question by the use and timing of the medication.

Dr Jeroen Swart, a South African physiologist, said that Team Sky should explain why Wiggins needed to take a strong corticosteroid before significant races.

"Although this isn't any evidence of any doping practice, it just is a little too far in terms of my comfort with respect to the ethical boundaries of the sport," Swart said.

"The first thing is just be very open and transparent about it. I would have liked to have seen an open press conference. But we haven't seen that."

Wiggins was granted the TUE because of grass allergies exacerbating his asthma.

In his autobiography, My Time, Wiggins reported illness before the 2011 Tour, but that was two days of diarrhoea.

He had not previously discussed his need for TUEs for triamcinolone acetonide injections and even claimed he had never had injections.

In his statement over the weekend, Wiggins said that had been a "passing comment" referring to the "historic (illegal) practice of intravenous injections of performance-enhancing substances".

Dr John Dickinson, head of the respiratory clinic at the University of Kent who has screened Team GB athletes for asthma, told the BBC that asthmatics could normally control their symptoms through use of inhalers.

"If they are well-controlled individuals they shouldn't need to apply for a TUE," he said.

Wiggins' TUE details were leaked by alleged Russian hackers, the Fancy Bears, who penetrated the computer system of the World Anti-Doping Agency (Wada).

Wiggins was shown to have been granted TUEs by the International Cycling Union for asthma inhalers prior to the three corticosteroid injections that he took days before the Tour campaigns in 2011 and 2012, and the Giro d'Italia in 2013.

Team Sky insist that only 12 TUEs have been granted to their riders since the team's formation in 2010, with only one in the past two years.

But Swart believes the Wiggins injections do leave many unanswered questions.

"Either they have prescribed it as a preventative medicine, which doesn't sit well with me, or he had such serious symptoms that they were completely uncontrollable," he said.

THE TIMES, LONDON, THE GUARDIAN