Not presidential elections and certainly not the plight of those fleeing the world's bloodiest conflict.

But the maker of Skittles has just delivered a brand management master lesson, according to one expert, after it was dragged into the heated debate around granting asylum to Syrian refugees.

On Tuesday, Donald Trump jnr, a top adviser to his United States presidential candidate father, tweeted a picture of a bowl of Skittles asking if his followers would take a handful if they knew that "three would kill you".

"That's our Syrian refugee problem," he said, suggesting some of the 4.8 million people who have fled Syria's brutal five-year civil war would kill Americans if granted sanctuary there.

The post drew swift condemnation from the UN High Commissioner for Refugees, which called it "dehumanising, demeaning and dangerous", and from social media users who heaped scorn on the analogy.

Then came the strong response from Wrigley, the company that makes Skittles.

"Skittles are candy. Refugees are people. We don't feel it's an appropriate analogy," a company spokesman told the Hollywood Reporter.

"We will respectfully refrain from further commentary as anything we say could be misinterpreted as marketing."

The same statement was later posted on Twitter by Mars Incorporated, the confectionary giant that owns Wrigley, and earned plaudits online. Many netizens pledged to buy packets of Skittles.

But not so small it fits in @realDonaldTrump's itty bitty hands.— Humorless Fem (@ahumorlessfem) September 20, 2016

Kim Johnston, senior lecturer in public relations at Queensland University of Technology, said the response was destined to be taught to her PR students in years to come.

"They were trying to distance themselves and make their position clear and they needed to do it in a way that would not keep that conversation going," Dr Johnston said. "They almost did a smack down."

She said Skittles' other options - staying silent and risking the appearance of giving tacit endorsement, or coming out too stridently and appearing to be capitalising on the situation - would have been damaging.

'Clever response'

"For a confectionary brand that is associated with rainbows and colourful places to eat lollies and happy things, being drawn into these social issues is very damaging, particularly when they haven't had a say as to what role they play," Dr Johnston said.

"That's why their response was so clever: they weren't offering an opinion or position on refugees."

It's not the first time Skittles has been thrust into the centre of a controversial issue. Unarmed teenager Trayvon Martin was carrying a bag of the lollies when he was shot dead in the US in 2012.

They became a symbol of the perceived racial injustices that underscored his death, piling up at makeshift memorials, being carried at rallies and mailed en mass to the local police department.

Skittles also kept an arm's length from the issue then, saying it would not want its "actions to be perceived as an attempt of commercial gain following this tragedy".

It emerged on Wednesday that the image used in Mr Trump jnr's original post was taken by a refugee who did not give permission for the photo to be used.

More than 4.8 million Syrians have fled the bloody conflict in their home country and registered as refugees, and another 6.1 million are internally displaced, according to the United Nations.

The US recently settled its 10,000th Syrian refugee this year and Australia granted asylum to 8640 people displaced by conflicts in Syria and Iraq last financial year.