Researchers have discovered the presence of smell receptors in human bronchi, which when activated by a scent resembling that of bananas can improve breathing and potentially alleviate asthma and allergies.

In a new paper appearing in the journal Frontiers in Physiology, a team of scientists explains how they detected two olfactory receptors – similar to those found in the nose – in the human airway smooth muscle cells (HASMCs) that line parts of the respiratory system. Given the involvement of HASMCs in allergic asthma, this finding could prove pivotal in the development of new treatments to manipulate the activity of these cells in order to reduce symptoms.

For instance, a chemical messenger called histamine is often released as part of the body’s immune response to invading pathogens. Though the primary function of histamine is to control inflammation, it can also cause HASMCs to contract, leading to breathing difficulties – which is what tends to happen when people experience asthma attacks.

However, the study authors found that one of the newly discovered olfactory receptors – called OR2AG1 – could be activated by the fruity scent of a chemical called amyl butyrate, causing HASMCs to relax. This, in turn, enables the bronchioles to dilate, reversing the effects of histamine and allowing breathing to return to normal.

The other receptor, called OR1D2, can be activated by an aromatic compound called bourgeonal – which is often used in perfumes – leading to the opposite effect, whereby HASMCs contract and breathing becomes problematic. This could explain why asthmatic people often experience flare-ups when they encounter certain perfumes.

However, a substance called undecanal was found to inhibit OR1D2, blocking this effect and allowing the muscles of the respiratory system to function as normal.

The researchers suggest that targeting smell receptors in the lungs could prove to be an effective strategy in the fight against respiratory diseases. In a statement, study co-author Hanns Hatt explained that “amyl butyrate may help improve airflow in asthma sufferers… It can probably counteract not only the effect of histamine, but also that of other allergens that make breathing difficult.”