The number of young children with Type 1 diabetes has risen dramatically in the last 20 years, a study suggests.
People with type 1 diabetes require insulin therapy
The number of under-fives with the condition increased five-fold - meaning it affected one child in every 1,000 by 2004, a study around Oxford found.
Other studies have revealed similar rises, suggesting the trend is true for the whole of the UK, Diabetes UK said.
The Bristol University team blame genes and environmental factors, including breastfeeding rates.
The number of under-15s with the condition almost doubled during the study, which focused on 2.6 million people in and around the Oxford region between 1985 and 2004.
Type 1 diabetes, also referred to insulin-dependent diabetes, generally develops in childhood and often runs in families.
In contrast, the far more common Type 2 diabetes tends to develop later in life and is largely linked to lifestyle factors such as obesity.
Of the estimated more than two million people with diabetes in the UK, around 250,000 have Type 1.
At least 20,000 children of school age in the UK have Type 1, according to the charity Diabetes UK.
Sign of the times
Lead researcher Professor Polly Bingley said the rate of childhood Type 1 diabetes was increasing all over Europe, particularly in the very young.
She said the increase was too steep to be put down to genetic factors alone.
"So it must be due to changes in our environment.
"This could either mean that we are being exposed to something new, or that we now have reduced exposure to something that was previously controlling our immune responses."
She suggested that fewer mums opting to breastfeed their babies might be a factor.
Another possibility is that children are being exposed to fewer germs, affecting the development of their immune systems.
"We now need to work to identify what these changes might be."
She presented her findings at Diabetes UK's annual conference.
Simon O'Neill, director of care, information and advocacy services for the charity, added: "Whilst 10 to 14-year-olds remain the largest group for diagnosis, the rise in cases found in children under five is worrying."