The group have been taught basic survival skills
Actor Chris Bisson received medical attention after falling over during his first day in the jungle for I'm A Celebrity... Get Me Out Of Here.
The former Coronation Street star slipped and suffered a blow to the head and cuts to his shoulder and ear as fellow contestants tried to kill a "deadly" spider.
Bisson, who was soon given the all-clear by a show doctor, is among 10 personalities competing over the next two weeks for the title of King or Queen of the Jungle.
The other contestants are Danniella Westbrook, Wayne Sleep, Phil Tufnell, Catalina Guirado, Antony Worrall Thompson, John Fashanu, Toyah Willcox, Sian Lloyd and Linda Barker.
They will be camping on the slopes of a remote volcano in southern Queensland, fending for themselves and living among jungle creatures.
The contestants decided to kill the spider after the offending creature was spotted amid the foliage.
I'M A CELEBRITY... FAVOURITES
Phil Tufnell - 3-1
Toyah Willcox - 4-1
Sian Lloyd - 6-1
Chris Bisson - 13-2
Linda Barker - 7-1
Source: William Hill
The contestants had decided it was just like one identified as poisonous during training.
After his fall, Bisson lay motionless on the ground for a few seconds before being helped up by his concerned camp-mates.
A spokeswoman for the ITV1 show which started on Monday said: "Chris was very shocked by the fall and
we called in a medic to check he was OK.
"Luckily he wasn't seriously injured and he is now back in camp."
The first day of the Ant and Dec-hosted show also saw the return of more familiar activities - most notably the Bushtucker Trial, which contestants must complete to win food.
Former footballer and Gladiators presenter John Fashanu was suitably mortified when he was nominated for the challenge, which involved pouring 10 boxes of bugs down his trousers.
Ex-Coronation Street actor Chris Bisson is the youngest of the group
He looked distinctly uncomfortable as worms, crayfish, stink beetles, cockroaches, stick insects and crickets swarmed over his skin.
Fashanu called the challenge to an end at the eighth box, which would have seen rats join the other creepy-crawlies.
Afterwards he said: "It was tough, they were biting and stinging. It wasn't nice at all - it was horrible.
"I'm pleased that I did it, the team need the food, but I do not want to do that again."
Monday night's public phone poll picked Catalina Guirado to face a crocodile-infested pit in an effort to secure more food for the group.
The camp security guards had a busy day - searching the celebrities for contraband.
Fashanu was found with a potato peeler, while cricketer Phil Tufnell had crisps and chocolate and dancer Wayne Sleep had sticking plasters.
Worrall Thompson, a chef, outwitted the guards by smuggling in some spices taped to his stomach.
Last year's winner of the surprise hit first series was veteran DJ Tony Blackburn, who has seen a resurgence in his career since the victory.
Each day, the contestants will have to nominate their least favourite jungle companion to face the public vote to leave the show early.
Tufnell is the bookmakers' favourite, with William Hill offering odds of 3-1, while former punk singer Toyah Willcox is second favourite at 7-2.
As well as surviving jungle life - and the company of each other - the celebrities will also have to undergo tasks to win luxuries.
Programme bosses, who are hoping for another ratings hit, have promised conditions will be harsher than last year.
The celebrities have spent several days at a nearby base camp learning basic survival skills in preparation for their outdoor adventure.