The study, published in the November/December issue of the Journal of Asthma (41(8), pp825-32), found that 60 children aged six to 18 years old were able to significantly reduce or discontinue their use of rescue inhalers more often than the placebo group.

The study also showed a significant reduction of inflammatory mediators called leukotrienes, which cause inflammation and bronchi constriction commonly associated with asthma.

"Treatment compliance is a great problem among the 4-5 million children under the age of 18 suffering from asthma,” said author Benjamin Lau from Loma Linda University in the US.

“This study demonstrates help for asthmatic children by a nutritional approach as compared to oral medication or rescue inhalers," he added.

Asthma incidence is climbing in many developed countries. In the UK, one in eight children has asthma and this figure has increased six-fold in the last 25 years, according to Asthma UK.

Pycnogenol, a proprietary mixture of water-soluble bioflavonoids extracted from French maritime pine, is known to have potent antioxidant activity and anti-inflammatory properties. These are thought to combat the inflammatory processes of the bronchi that cause them to constrict and swell, making breathing difficult for asthmatics.

Previous studies have shown the supplement to be effective in decreasing asthma symptoms among adults, as well as helping a number of other inflammatory conditions.

In the new research, Pycnogenol showed benefits on a number of different parameters. Breathing improved after only one month and continued with further treatment, and the severity of asthma symptoms also decreased the longer participants took the supplement.

Pycnogenol also dramatically reduced and in several cases eliminated the children's dependence on a rescue inhaler, which is used to rapidly dilate the bronchi during an asthma attack.

“These recent results…position it as a key player in the management of mild to moderate childhood asthma," said Lau.