Everyone has experienced it at least once. A nasty cold blocks the nose, you can’t smell anything and all food tastes bland.

“You need your sense of smell for the sensation of fine aromas,” said Thomas Hummel from the University of Dresden, an expert on smell and taste disorders. But while the sense of taste returns after the cold goes away, some people must live without this sense. There are various reasons for it and treatment is often difficult.

“While the sense of smell is mediated through one cranial nerve, there are three involved with the sense of taste,” said Karl-Bernd Huettenbrink from the German Society of Oto-Rhino-Laryngology, Head and Neck Surgery. The oral sense of touch with the trigeminal cranial nerve also plays a role in sensory perception. An example of that is the impression that chillis are spicy.

People used to assume that taste buds are only on the tongue, but it’s been proven that they exist throughout the entire mouth and throat. And the taste of a food is also made up its appearance, texture, spiciness, temperature and fat content.

“Isolated taste disorders are rather rare,” said Huettenbrink. In most cases, people who say they can’t taste anything have problems with their olfactory system.

It’s difficult to diagnose the problem. Doctors differentiate pure taste disorders between damage to the taste buds, damage to cranial nerves or an impact to the brain - for example a fall on the head, a brain tumour or a psychiatric illnesses. The sensory cells can be damaged after an infection, through radiotherapy or chemotherapy, or even hundreds of different medications.

The three cranial nerves that control the sense of taste can be affected by a broken skull base or ear or throat operations. Even diabetes or a thyroid disorder can spoil the sense of taste.

Hummel and his colleagues examined 4,680 patients, 491 of whom had a pure taste disorder. For one-third of them it could not be determined from where the issue came. For a quarter of them, it was the consequence of an injury or accident. Another quarter came from a mix of disorders including medications. The complaints began for 15 per cent after an operation.

Until now, the medical world has had very few means available to help patients with pure gustatory disorders. “By leaving out or changing medication, you can tell if that’s the reason and then treat it,” said Hummel. Therapy could include the use of zinc. “We have hints that zinc acts better as a placebo, but we don’t know the exact reasons why that is.” There are more chances if the olfactory sense is the reason for the taste problem. “Olfactory cells can build up in the upper part of the nasal cavity. That is possibly a reason why the sense of smell slowly returns for many patients as we know from a cold,” said Hummel.

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