It is one of Covid’s most distinctive and curious symptoms: the loss of the sense of smell, which blights more than half of sufferers.
Among the many things the virus attacks are the receptor cells in the nose, affecting their ability to function properly.
While most people recover in a few weeks, for roughly one in ten the problem, called anosmia, lingers for a month or more.
Now scientists have stumbled on a potential treatment for reawakening the senses: Vitamin A.
Vitamin drops to waken sleeping cells
There is already some compelling evidence that Vitamin A nose drops could be the anosmia treatment patients are desperate for.
In April last year, a group of German doctors at the University of Dresden conducted a study similar to the proposed British one, trialing the drops in a group of patients over eight weeks.
Half were given the drops alongside ‘smell training’ – which involves sniffing strong scents every day, such as rose and coffee, to stimulate nerve cells inside the nose.
The other half were given smell training alone, and no drops.
After eight weeks, 37 per cent of those using the drops reported a significant improvement in smell detection, compared with 23 percent of the control group.
A substance in the vitamin – retinoic acid – is known to repair damaged DNA in cells, which may explain the effect.
Take a good sniff at some strong odors
Doctors have long debated the effectiveness of smell training for regaining senses. Some studies show it to be effective, while others have shown limited benefits.
However, Prof Philpott says that the research conducted by his team at the University of East Anglia suggests it is worth trying.
A study of 140 anosmia patients found that sniffing at least four odors – including lemon, rose and eucalyptus – twice daily for two months could significantly improve subjects’ sense of smell.
Prof Philpott suggests buying rehabilitation kits online, or using strong-smelling spices or other pungent ingredients that are found in most kitchen cupboards.
Smother everything in tomato sauce
Perhaps the most wretched element of losing your ability to smell is the associated loss of taste.
Prof Smith says his patients report a host of strange sensations alongside this – from different foods all tasting the same to phantom tastes, such as rotting rubbish.
Experts say that this is mainly due to the virus’s effect on the nasal cells.
‘While some may be able to detect sweet or salty, a depth of flavor comes from breathing in the scents of food as we eat,’ says Prof Philpott.
‘If the smell disappears, everything taste odd or flavorless,’.
But there is one basic taste that shines through particularly well: meaty, savouriness called umami.