Sales of rosemary have boomed after research found the herb could help students studying for exams, figures suggest.

Holland & Barrett said it has ordered extra stocks of rosemary essential oil after it saw sales almost double compared with the same point last year.

The health food retailer believes the surge in demand could be due to a recent study published by Northumbria University which showed that exposure to the smell of the herb can help to boost memory.

New figures from Holland & Barrett show sales of rosemary oil in the UK, Ireland and online in the week the study was released were up 187% when compared with the same week last year, and up 270% compared with the week before the research was published.

The increase in sales comes as teenagers prepare to sit their GCSEs, A-levels and Scottish Highers in schools, and university students prepare for their end of year exams.

"Following the Northumbria University research pointing to a positive link between rosemary and memory in students, we saw a sharp rise in customer demand for our 100% pure Miaroma Rosemary Essential Oil, with sales increasing by almost 300 per cent on the previous week," a spokesperson for Holland & Barrett said.

"As exam season continues, we have increased provision in store to meet demand and our trained associates are on-hand as always to answer any questions customers may have about the benefits of aromatherapy and essential oils."

The exam season is about to get underway. Credit: PA

The Northumbria University study saw 40 children aged 10 and 11 given different mental tasks in one of two rooms, one that had rosemary oil diffused in it for 10 minutes and one that had no aroma.

Researchers found the children in the rosemary scented room gained higher scores than those in the non-scented room, with the biggest difference in scores in the test that asked the youngsters to recall words.

Study author Mark Moss said at the time the research was published that the reasons why rosemary has an effect is open to debate.

"It could be that aromas affect electrical activity in the brain or that pharmacologically active compounds can be absorbed when adults are exposed," he said.

"We do know that poor working memory is related to poor academic performance and these findings offer a possible cost-effective and simple intervention to improve academic performance in children."