A charity fighting to stop asthma said this increase is “extremely distressing” and blames a lack of care, and complacency about the condition.
Latest figures reveal that from April 2016 to March 2017 the area had a rate of 362 asthma-related admissions for every 100,000 children, up from 260 five years earlier.
During the 12 months, 113 people under 19 were admitted to hospital – 57 boys and 56 girls.
Asthma is a common lung condition that can cause breathing difficulties.
It affects people of all ages and usually starts in childhood.
There is no cure, but there are simple treatments that can help keep the symptoms under control.
In England, the rate of asthma-related admissions in 2016-17 was 203 in every 100,000 children, 4.5% higher than five years earlier.
Samantha Walker, director of research and policy at Asthma UK, said: “It is extremely distressing that the rate of children and teenagers admitted to hospital because of their asthma is on the rise.
“While the reasons for this rise are not entirely clear, a lack of basic care – including an asthma action plan, inhaler technique check and annual asthma review – could be to blame. We also know that a lack of understanding of the seriousness of asthma could also play a part.
“Parents concerned about their children’s asthma health should make sure their child takes their medicines, follows a written asthma action plan and attends an annual review with a GP or asthma nurse.”
Boys are more likely to end up in hospital due to asthma than girls. The rates across England show 234 admissions for every 100,000 boys compared to 170 for girls.
Asthma is caused by inflammation of the breathing tubes that carry air in and out of the lungs.
Allergies, colds, smoking, exercise and even cold air are among the most common triggers of asthma attacks.
Asthma UK said there is not enough scientific evidence to suggest air pollution is linked to asthma despite anecdotal reports that it can trigger the condition.
According to NHS estimates, asthma attacks kill three people in the UK every day.