Helen Buniak describes her son Lee as a "Jekyll and Hyde" character.
"He'd be a lovely, good little boy most of the time, but then he would become suddenly very aggressive, with these massive tantrums."
Lee's behaviour improved with a new diet
For the first eight years of his life, she said, she had no idea of the reason behind it.
Then she noticed a coincidence.
Lee had five "episodes" in close succession, and Helen, from London, realised that each one had followed the birthday of a classmate - which meant the handing out of sweets by parents at the school gate.
"I realised that there was something in those sweets that was making him behave like that," she says.
No-one had mentioned the possibility that food additives or ingredients might be to blame, and she turned to the Hyperactive Children's Support Group for health.
They recommended a diet which involved removing foods which included additives, then gradually reintroducing them.
"Lee had a normal diet, but there were so many things that had additives - meat pies and bacon as well as sweets, fizzy drinks and crisps."
The effect was immediate, she says.
"Straightaway his behaviour improved - and it wasn't just his behaviour, his learning improved as well."
Now 10, although Lee is much better, he still has occasional "episodes".
Helen says that these can still be attributed almost entirely to food.
"Unfortunately, you can't completely avoid additives - sometimes you have to eat when you're out and about, and he still goes to parties."
She says that his doctors have been less easy to convince about what she believes is the root of the problem.
Lee has never been referred to a dietician.
"They just don't believe me. I've kept a food diary - I've got all the evidence, but only last week one was telling me he didn't think food additives were to blame.
"One even suggested that Lee had a phobia about sweets, and that was why he was misbehaving. When was the last time you saw a child with a phobia of sweets?"
You should always consult your doctor before making major changes to your or your child's diet.