His mum thought perhaps he had eczema, so she decided to take her seven year old to her family doctor near her home in Rossington, Doncaster.
But within 24 hours he was in Sheffield Children's Hospital, starting treatment for leukemia.
Mum Emma Fraser said: "He had a rash all over his body - my first thought was that he had eczema."
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But it was much more serious - he had been diagnosed with acute lymphoblastic leukemia, a form of blood cancer.
"I took him to the doctor, and he was referred to a pediatrician the same day. They ran tests, and then rang me the next day to go in. We went into hospital at Sheffield Children's Hospital, and we ended up staying there for a week. He started treatment on the Monday.
"It's been very difficult, and the situation is hard because I have another two children, and I've not been able to see them as much as I'd want to."
It has been a tough period. Tommy didn't react well to his initial chemotherapy and was switched to a different sort.
He suffered a further setback when he picked up a superbug. It appeared as a set of scabs around his lips. But he responded well to antibiotics after being taken back into hospital for treatment.
Emma is worried - it is a serious illness. But she was grateful for the speed with which the doctors sprang into action when they realised how ill her son was.
"I was really pleased with the speed with which they dealt with everything," she said. "But I was mortified to find out he had leukemia.
"Leaukaemia has always been my biggest fear. Tommy's dad's little brother had the same, and he died at the age of four. That was around the time I was pregnant with Tommy.
"When Tommy got referred I think I perhaps already knew, I had that gut feeling. When they rang back I knew it was bad
"It is every parent's nightmare, but you don't realist just how many children are going through the same thing until you go the the children's hospital in Sheffield. We have met people who have come through the other side. Treatment goes on for over two years and they say the first year is the worst. The children who are further down the road have been inspirational to us."
Tommy has two younger brothers, Charlie, aged five, and two-year-old Travis.
"They're coping with the situation," said Emma, aged 26, from Ormond Way. "When Tommy was first diagnosed, Charlie thought that he didn't want to play with him, and felt like he had lost his big brother for a bit, but he's got him back a bit now.
"Tommy has been very brave, and I'm really proud of him."
Tommy has started to return to school. At present he returning to lessons at Grange Lane School for an hour in the afternoon when he feels well enough. Emma does not want him to miss too much school and is wanting him to start to return for an hour every day.
Emma has been moved by the way the community in Rossington and Doncaster has rallied round to support her.
Several events have been held to raise money to help the family.
They have included an Easter themed fund day at the Poacher pub on Radburn Road, Rossington, as well as a charity night at a pub in Wheatley.
There has also been a charity football match at Rossington Main.
Another event is in the pipeline at Rossington Miners Welfare.
Emma said she was grateful for the support she had received, which has helped make life easier for the family.
On one occasion, the family drew on the fund that has been set up to pay for a taxi for relatives including Tommy's dad, Daniel, to take them to the hospital when an emergency arose there. It has also bought Tommy a tablet to use and to take him on a trip to the Yorkshire Wildlife Park.
Emma's big hope is to be able to take Tommy onto an aeroplane. He loves aeroplanes, and says his favourite type of plane is the Vulcan bomber. She said she thought Tommy would be delighted if anyone was able to offer him a flight when he is fit enough.
She said: "If there is enough left in the pot, I would love him to be able to go in a plane when he is well enough," she said.
Before he was taken ill, he also enjoyed playing football and playing car games on his video games console His favourite team is Manchester City and his favourite player is Sergio Aguero.