Parents have been warned not to give the popular herbal cold remedy echinacea to children under 12 amid fears of severe allergic reactions.
The Medicines and Healthcare products Regulatory Agency (MHRA) said the small risk of a reaction outweighed any perceived benefits.
It said that older children and adults could continue to use the herb, and that the warning was a precautionary measure.
In under 12s, the MHRA said there was a heightened risk of allergic reactions which could include rashes, hives, difficulty in breathing and even anaphylactic shock, which is potentially fatal.
Speaking to the BBC, Richard Woodfield, head of herbal policy at the MHRA, said: "This is not a serious safety issue, but parents and carers need to be aware that children under 12 could have a low risk of developing allergic reactions.
"The measures being taken are precautionary in nature. Parents should not worry if they have given echinacea to children under 12 in the past."
There will now be warning labels on licensed products containing echinacea. Research in the US has found the herb can decrease the odds of catching a cold by 58 per cent.
Do you use echinacea as a cold and flu remedy for yourself or your children?