British asthmatic children are needlessly being prescribed antibiotics despite evidence they no more need them than other children.
They are nearly twice more likely to be prescribed antibiotics, compared to children who do not have the condition.
Over prescribing antibiotics has been blamed for the rise in superbugs that are resistant to the life saving medicines.
And giving children them could put them at risk of difficult to teat illnesses later in life.
Dutch scientists said the over prescription could be because asthma symptoms are being mistaken for a respiratory tract infection.
Or they are being given as a preventative measure against guidelines.
Dr Esmé Baan at the Erasmus University, Rotterdam, said: "Asthma is a common and ongoing condition, and it has symptoms that could be mistaken for a respiratory tract infection.
"However, international and national guidelines clearly state that antibiotics should not be given for a deterioration in asthma symptoms, because this is rarely associated with a bacterial infection.
"Inappropriate use of antibiotics can be bad for individual patients and the entire population, and makes it harder to control the spread of untreatable infections."
The study looked at 1.5 million British children including around 150,000 with asthma, and a further 375,000 from The Netherlands, including around 30,000 with asthma.
It looked a medical records for antibiotic prescriptions and compared the two European countries as both follow the same international guidelines on asthma treatment
It found children with asthma were approximately 1.6 times more likely to be prescribed antibiotics than other children and antibiotic prescription rates were almost two-fold higher in the UK overall.
Amoxicillin was the most commonly used antibiotic.
In the UK there were 374 prescriptions per 1,000 children with asthma per year, compared to 250 per 1,000 without asthma.
In The Netherlands it was 197 per 1,000 and 126 per 1,000 respectively.
Low antibiotic use
The Dutch have one of the lowest antibiotic use in the world so scientist fear it could be far worse in countries where antibiotic use is high such as Italy, Spain, Portugal and Greece.
Dr Baan said: "Antibiotics should only be given when there is clear evidence of a bacterial infection such as for pneumonia.
"However, we saw that, in children with asthma, most of the antibiotic prescriptions in children were intended for asthma exacerbations or bronchitis, which are often caused by a virus rather than bacteria.
"It can be difficult for a GP to differentiate between a deterioration in asthma symptoms and a bacterial respiratory infection.
"We think this might be leading to more antibiotic prescriptions in children with asthma.
"Children with uncontrolled asthma can face difficulties over several years, for example it can affect their ability to play and take part in sport, they may have more days off school, or experience disturbed sleep.
"We don't want to compound this with prescribing drugs that won't help and may be harmful.
"Of course, sometimes antibiotics are needed, but we should be careful and only prescribe them when they are really required.
"In general, we should discourage GPs from prescribing unnecessary antibiotics or run the risk of more drug-resistant infections in the future."
The study was presented at the European Respiratory Society International Congress 2017 in Milan.