Lachlan Canak thought he could sneak a treat before school without anybody finding out.

But the 7-year-old didn't realise the lolly in question would send him running to his mother in pain after burning a hole in his tongue.

The Sydney boy's mum, Hayley, was shocked when she discovered the damage a Sour Warhead lolly did to his tongue last week, and posted a picture on Facebook as a warning to other parents.

"I really felt the need to share this photo: this happened after he was eating sour war head candy. It has burnt a hole in his tongue," Hayley wrote.

The mum said she "felt sick" when she first saw her son's tongue.

Other parents were equally concerned, with many saying they would throw out similar lollies after seeing Lachlan's wound.

The lollies which burned Lachlan's tongue were Warheads Juniors Extreme Sour. They contain malic acid and are marketed as an "extreme candy" by US company Impact Confections. The packaging states the lollies are appropriate for children aged 4 and older.

Various lines of Warheads extreme sour candies are also available in New Zealand. What appears to be the equivalent to the one tried by Lachlan is sold here as Warheads Mini Size Extreme Sour candy.

The Warheads hard sweets come with a warning that "eating multiple pieces within a short time period may cause a temporary irritation to sensitive tongues and mouths." Some other brands of sour lollies also have warnings that excessive consumption might cause blistering of the tongue.

However Hayley said the injury on her son's tongue was more than an "irritation".

The family was very relieved to see the inflammation had gone down by the end of Lachlan's school day and his tongue was looking a lot better.

"However it is really hurting," Hayely said. "I had to blend his food for dinner and even that hurt him."

Lachlan is not the first person to suffer similar injuries when eating the sour lollies. Several people have posted complaints on the Warheads Facebook page about similar incidents.

"Parents beware. My daughter ate this product and this is the result," one angry US mother posted along with a picture of her child's burnt tongue.

"The company went back and forth with me with no resolution. They kept using the words 'mild irritation'. My daughter couldn't eat or drink for days after this incident. Layers of her tongue were burnt off from the acid in this 'candy'."

A US man whose young sister's tongue was burnt from eating Warheads said he thought it was a 'disgrace' that the warning about the potential dangers of the lollies was in such small print.

"[My sister] experienced pain when eating and drinking. Only afterwards, when we decided to read the packet, did we see a tiny disclaimer stating that eating multiple can cause damage to the mouth," the man posted on the Warheads page.

"No one reads/should need to read the fine print of a confectionary item to determine it's safety for consumption, unless one suffers from nut allergies/etc. I feel that print as small as that, on the back of the packet as well, is unacceptable and something needs to be done."

Despite the potential for injury, Warhead candy fans are known to undertake "Warhead challenges" during which they eat as many of the lollies they can tolerate. They often post videos of their performance to YouTube.

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