Parents have been warned of the effects of food additives on their children's behaviour after new research found a possible link to hyperactivity.
Many additives are found in food
A Food Standards Agency (FSA) study of 300 random children found they behaved impulsively and lost concentration after a drink containing additives.
The FSA now says hyperactive children might benefit from fewer additives.
But experts said drugs rather than diet changes could improve behaviour more effectively in the most severe cases.
Dr Andrew Wadge, the FSA's chief scientist, said: "We have revised our advice to consumers: if a child shows signs of hyperactivity or ADHD then eliminating the colours used in the... study from their diet might have some beneficial effects."
He did say though there were many factors associated with hyperactivity including genes, being born prematurely, environment and upbringing.
Sunset yellow (E110) - Colouring found in squashes
Carmoisine (E122) - Red colouring in jellies
Tartrazine (E102) - New colouring in lollies, fizzy drinks
Ponceau 4R (E124) - Red colouring
Sodium benzoate (E211) - Preservative
Quinoline yellow (E104) - Food colouring
Allura red AC (E129) - Orange / red food dye
The FSA has met representatives of the UK food industry to talk about the study's implications, but food safety campaigners say it has not gone far enough.
Emma Hockridge, of the Soil Association, said the FSA should be taking a leading role in addressing the issue by undertaking initiatives to prevent the development of hyperactive disorders, through new policies to limit food additives.
The Food Commission called on food manufacturers to voluntarily remove additives from their products.
A spokesman said: "These artificial colourings may brighten up processed foods and drinks but it appears they have the potential to play havoc with some children's behaviour."
Julian Hunt, from the Food and Drink Federation, said they accepted the FSA's advice but said the tests did not represent how additives were used normally.
"Manufacturers are very aware of consumer sensitivities about the use of additives in food and drink products. It is important to reassure consumers that the Southampton study does not suggest there is a safety issue with the use of these additives."
This is not the first study to make a link between additives and hyperactive behaviour, but a wider age range of children were selected than in previous research, and not all had behavioural problems.
The Food Standards Agency paid for Southampton University researchers to examine whether giving additives to a group of ordinary three-year-olds and eight or nine-year-olds had any effect on their behaviour.
The children were randomly given one of three drinks, either a potent mix of colourings and additives, a drink that roughly matched the average daily additive intake of a child of their age, or a "placebo" drink which had no additives.
Their hyperactivity levels were measured before and after the drink was taken. Mix "A", with the high levels of additives, had a "significantly adverse" effect compared with the inactive placebo drink.
The older children showed some adverse effects after the second, less potent mix, although the response varied significantly from child to child.
Lead researcher Professor Jim Stevenson said the study, published in the Lancet, showed that certain mixtures of artificial food colours, alongside sodium benzoate, a preservative used in ice cream and confectionary, were linked to increases in hyperactivity.
He added: "However, parents should not think that simply taking these additives out of food will prevent hyperactive disorders.
"We know that many other influences are at work but this at least is one a child can avoid."
He said it was not possible to say which of the ingredients in the additives cocktail affected the children.
Between 5% and 10% of school-age children suffer some degree of ADHD - attention deficit hyperactivity disorder - researchers suggest, with symptoms such as impulsiveness, inability to concentrate and excessive activity.
More boys than girls are diagnosed with the condition, and children with ADHD can struggle academically, often behaving poorly in school.
Andrea Bilbow, from ADHD support group ADDISS, said most parents of children with ADHD had tried diet changes.
While more than half had reported some improvement, this tended to be modest when compared with the effect of medication, she said.
"In some respects the question of food additives is a little bit of a red herring.
"While in some cases, a poor diet could make ADHD even worse, a better diet is not going to make it much better," she said.
And Dr Paul Illing, of the Royal Society of Chemistry, raised questions about the validity of the study, saying extrapolating from the small study population to the general public was very difficult.