Hillary Clinton suffers from coughing fit and jokes ‘every time I think about Trump I get allergic’

Democratic candidate laughs off frog in her throat, but it will fuel increasingly vocal band of conspiracy theorists who believe she is ill

For many Democratic voters, Donald Trump is toxic. For Hillary Clinton he is allergenic.

As she broke down in a coughing fit during a Labour Day stump speech attacking the Republican candidate, she joked: “I've been talking so much. Every time I think about Trump I get allergic.”

Tim Kaine, her running mate standing behind her, looked delighted as he clapped in response while the audience laughed at her quick thinking.

However, the coughing bout set off the conspiracy theorists that lurk in darker corners of the internet and on shock jock talk radio and TV shows who are convinced Ms Clinton, 68, is hiding a serious disease.

Critics also joked that it was a response to meeting journalists on her plane on Monday.

She has been criticised frequently for failing to hold a full press conference all year but held a brief question and answer session with reporters who joined her on a new campaign 737.

Ms Clinton said the release of her doctor’s letter earlier in the campaign - a response to the mounting conspiracy theories - explained the frog in her throat.

“I'm not concerned about the conspiracy theories. There are so many of them that I've lost track of them,” she told journalists.

“One thing you know from my doctor's letter is I have seasonal allergies.”

A number of recent surveys have shown Mr Trump pulling level with Ms Clinton in national polls although the quirks of the US electoral college system suggest the Democratic candidate is a clear favourite to win the November