Every year there are spikes in hospital admissions for attacks during September, said Asthma and Lung UK.
Children with the condition are exposed to more triggers, such as cold viruses, when they return to school.
In 2016 – the most recent data available – 1,795 children were admitted in England in that month, up from 435 in August.
Rebecca Grandison, 42, from Cheshire, “dreads” rushing her son Wilfred, seven, to hospital almost every September.
She blames the fact he “mixes with other children who have coughs and colds” and breathes in cold air in the playground.