It sounds harmless enough. But the latest internet challenge children and teens are sharing with their friends is very worrying. It involves placing salt and ice on their skin which gives a burning sensation - the challenge is to see how long you can withstand the pain. Such videos and photos are then being shared with pals. The main problem is that ice and salt cause a chemical reaction similar to frostbite as it reduces the temperature of ice to minus 17 celsius. The challenge first started in the US a few years ago but has recently seen a resurgence in the UK with the hashtag #iceandsaltchallenge The shocking pictures show painful looking scars and in some cases, the burns were so bad that doctors had to use skin grafts to treat the injuries. This week a children's charity warned parents and teachers over the incidents and asked them to be vigilant. One mother, from Fife, told the Sun Newspaper that her daughter had been left permanently scarred by her salt and ice challenge burns.

 "It does not hurt at the time, however as you can see in the picture is causes lasting damage."