Vitamin A: How nasal drops could help Covid sufferers regain their sense of smell

A new University of East Anglia study will investigate the impact on those left with long-term anosmia or parosmia after recovery from coronavirus. But how would it work?

A patient undergoes ‘smell training’ as part of her recovery from Covid-19 (Shutterstock)

A new study will examine the effect of vitamin A nasal drops on those who have lost their sense of smell after contracting Covid-19.

Anosmia, or smell blindness, is one of the key symptoms of the respiratory disease, alongside loss of taste, persistent coughing and high temperatures.

In some cases, a sufferer’s ability to detect smells may return naturally after their recovery from the initial illness, but others have reported being left with the condition for much longer.

Alternatively, patients might experience parosmia as a consequence of Covid, which means their scent associations are suddenly realigned so that ordinary tap water begins to smell like sulphur, for instance.

Now the “Apollo trial” being carried out by the University of East Anglia (UEA) at the the James Paget Hospital’s Smell and Taste Clinic in Great Yarmouth, Norfolk, is seeking to investigate the impact of vitamin A drops over 12 weeks on those who have recovered from coronavirus but been left unable to pick out scents and fragrances.

The fat-soluble vitamin, present in dairy and some vegetables and available in supplement form, is known to boost the immune system and have a beneficial impact on eyesight and the skin.

Cheese, eggs, oily fish, fortified low-fat spreads, milk, yoghurt and liver products are all good sources of the vitamin, according to the NHS, as are spinach, carrots, sweet potatoes, red peppers, mango, papaya and apricots.

Adults men aged 19 to 64 need 700 micrograms of retinol units per day and women in the same age bracket 600 micrograms, the health service recommends.

The UEA said in a statement that research in Germany had indicated that vitamin A might also be of assistance to those suffering from the legacy of Covid and that its forthcoming study would “explore how this treatment works to help repair tissues in the nose damaged by viruses”.

The institution expressed optimism that its findings “could one day help improve the lives of millions around the world who suffer from smell loss, by returning their fifth sense”.

Lead researcher Professor Carl Philpott from UEA’s Norwich Medical School said: “We want to find out whether there is an increase in the size and activity of damaged smell pathways in patients’ brains when they are treated with vitamin A nasal drops.

“We will look for changes in the size of the olfactory bulb - an area above the nose where the smell nerves join together and connect to the brain. We will also look at activity in areas of the brain linked to recognising smells.”

The study hopes to uncover a new path forward after a report published in the academic journal International Forum of Allergy & Rhinology in April argued against the use of steroids as a restorative treatment.

Professor Philpott said there was “very little evidence” steroids could help and threatened a number of “potential side effects including fluid retention, high blood pressure, and problems with mood swings and behaviour”.

Rather than anti-inflammatories, some of the participants in the UEA project will receive the drops while others will be treated with the current recommended alternative: “smell training”.

This will see them sniff four distinctive odours like rotten eggs, citrus fruits and roses at least twice a day for the duration of the study period in order to effectively retrain their noses to interpret flavours.

Brain scans will subsequently be used to monitor whether the treatments have succeeded in repairing the injured olfactory pathways.

This method “aims to help recovery based on neuroplasticity - the brain’s ability to reorganise itself to compensate for a change or injury,” Professor Philpott said.

The study is being funded by the National Institute for Health Research and will begin recruiting participants in December, with anyone interested in taking part advised to seek a referral from their GP.