Jimmy Fallon ruffles Donald Trump hair on The Tonight Show

Donald Trump found himself on the receiving end of Jimmy Fallon's physical humour last night during an appearance on the comedian's late night talk show.

The Republican presidential nominee has often been mocked for his hair, and Fallon found himself unable to resist messing up Trump's carefully coiffured hairstyle.

"The next time I see you, you could be president of the United States," Fallon told the New York billionaire.

"I just wanted to know if there's something we could do that's just not presidential. Can I mess your hair up?"

Trump agreed, allowing Fallon to vigorously ruffle his hair, as the audience cheered loudly.

The controversial presidential hopeful appeared to take the media coverage of the moment in good humour on Twitter.

During the interview, Trump also spoke about his campaign, saying the experience had been "grueling but at the same time very satisfying".

In reference to his comments about Hillary Clinton's pneumonia diagnosis, Fallon asked Trump if he had ever been sick.

"Is this wood or formica?" he asked of Fallon's desk, before pretending to knock on it and say that he had never been sick.

Trump's hair has been the subject of an ongoing fascination with the media and the public.

In a 2011 Rolling Stone magazine, Trump shared his in-depth hair routine, saying he used Head and Shoulders shampoo and lets his hair air dry for an hour.

"Do I comb it forward? No, I don't comb it forward," he said.

"I actually don't have a bad hairline," Trump added. "When you think about it, it's not bad.

"I mean, I get a lot of credit for comb-overs. But it's not really a comb-over. It's sort of a little bit forward and back. I've combed it the same way for years. Same thing, every time."