Japan's famous matcha could reduce sneezing in people with nasal allergies

There's now another reason to love Japan's famous matcha: a study in mice suggests that the green tea powder could reduce the need to sneeze in people with nasal allergies.

Matcha is a bright green powder made from specially-grown green tea leaves that are dried and ground. It's used both for making tea and as a flavouring in a wide range of products. Previous research has shown that the tea contains high levels of biologically active compounds, including antioxidants and amino acids, and its use is linked to a range of health benefits, such as improved heart and brain function, and reduced inflammation.

Professor Osamu Kaminuma, from the Research Institute for Radiation Biology and Medicine at Hiroshima University in Japan, was particularly interested in matcha's effects in people with allergic rhinitis, more commonly known as hay fever. "Human studies suggest green tea may relieve allergic rhinitis, but how it works is unclear," Kaminuma said.

In an early access paper published March 5 in npj Science of Food, Kaminuma and colleagues reported that mice engineered to experience hay fever symptoms were given matcha tea 2-3 times a week for over five weeks and an additional dose of tea 30 minutes before being exposed to an allergen that would trigger their allergic rhinitis symptoms.

The team found that the mice sneezed much less than expected with the matcha treatment, but perhaps more interesting was the finding that the matcha didn't appear to have any effect on the allergic responses dependent on immunoglobulin E (IgE), mast cells, and T cells.

IgE antibodies that bind to mast cells are central to allergic reactions, triggering the release of histamine and other inflammatory chemicals. Mast cells drive the early phase of the allergic response, while T cells orchestrate longer-term immune processes, including IgE production.

Oral matcha reduced sneezing without clearly changing major immune markers. Instead, it strongly suppressed brainstem neuronal activation linked to the sneezing reflex." 

Professor Osamu Kaminuma, Research Institute for Radiation Biology and Medicine, Hiroshima University

The group looked at the activity of a gene called c-Fos-an indicator of neurological and behavioural responses to an intense stimulus like being exposed to a hay fever allergen-in the ventral spinal trigeminal nucleus caudali, which is the region of the brain involved in sneezing. They found that when mice were experiencing hay fever, the expression of the c-Fos gene increased, but treatment with matcha reduced expression levels almost back down to normal.

The next step is to study whether these effects also occur in humans. "The goal is an evidence-backed, food-based option that complements standard care for allergic rhinitis symptoms," Kaminuma said.