Smell and taste disorders after brain injury

I'm here to talk to you about the impact that smell disorders can have on health, well-being, and safety following a head injury. We'll also talk about taste as part of that conversation as well.

Duncan set the charity up in 2012 because there was nobody out there to help him after he lost his sense of smell. He set it up with Professor Carl Philpot, whose specialist area is around smell and taste. We cover three areas as a charity: education, support and information, and research. We want to transform society's understanding of the importance of both smell and taste and hopefully transform the lives of those actually affected by these disorders.

Olfactory dysfunction (smell disorders) is common following trauma to the head and occurs in approximately 20% of traumatic brain injury cases. Approximately one in two patients with an olfactory deficit following a head injury are actually unaware of this sensory impairment.

While I am here to talk about head injuries, there are other causes as well. COVID-19, viral infections, cold and flu, nasal disorders, allergies, the aging process, certain medications, and operations can all have an impact. Neurodegenerative diseases like Alzheimer's, Parkinson's, and multiple sclerosis can also cause our sense of smell and taste to change; in fact, there is evidence that losing the sense of smell can be a very early warning sign for Alzheimer's and Parkinson's. Exposure to toxins, surviving a stroke, epilepsy, idiopathic causes, and congenital conditions (being born without the sense) are also factors.

If you have lost your sense of smell or taste, you realize how important these senses are. Not being able to smell makes it feel like you are in a bubble because you cannot smell the environment around you. There are also dangers, such as not being able to smell smoke from a fire or a gas leak. Subconsciously, we also bond with family and friends through our sense of smell. It is a neglected sense because it is not one we talk about, and there isn't specific training in the NHS unless it is your specialist subject.

Regarding smell disorders, anosmia is the complete inability to smell, while hyposmia is a reduced ability. Parosmia is where people have distorted smells; for example, food might smell like sewage or beauty products like burnt rubber. Phantosmia involves phantom smells, where someone smells something that isn't there, such as a permanent smell of burnt toast. Hypersensitivity (hyperosmia) is where things smell much stronger; this can also affect neurodiverse individuals with ADHD and autism.

Taste disorders involve the taste buds on the tongue. You can have a smell disorder and still taste, or a taste disorder and still smell. We have five basic tastes: sweet, salt, sour, bitter, and savory. When we eat or drink, we are actually smelling the food through the back of our throat, which goes up to our olfactory bulb. That process is where we get the flavor for our food. If someone's smell is gone completely, they won't get any flavor from their food, though they may still get the basic tastes on the tongue.

If your smell is impaired, you may not be able to smell a gas leak. People may stop doing things they enjoy, such as cooking, gardening, or walking, because they don't get the same pleasure. If somebody has cognitive impairment and they turn the gas on but forget to light it, they may not notice the gas. Similarly, when cleaning, they may not be aware of how strong the fumes are from cleaning products. You might see changes to personal hygiene due to anxiety about how they smell to others. It is also difficult to tell if food has gone off, which can lead to the risk of food poisoning.

Regarding nutrition, if someone's smell is impaired and they get no flavor, they may be drawn to things they can taste on their tongue, like very salty or sweet foods, or processed foods. Some people stop eating altogether because they lose the pleasure in food. Smells also trigger memories, so losing that sense can mean those memories are not triggered.

All of these factors affect nutrition, physical health, and relationships. It can lead to isolation if people do not want to engage socially over meals. Frustration often occurs with family members who do not understand the experience.

To stay safe, anyone with an impaired sense of smell is classed as vulnerable and can be registered on the Priority Services register. If you have cognitive impairment, a locking cooker valve can be fitted free of charge by gas distribution networks. It is crucial to have smoke and carbon monoxide detectors, and natural gas detectors are also very important. Some gas appliances in certain networks can be serviced for free to ensure there are no leaks.

For food safety, if you live with someone, ask them to check if food is safe to eat. Labeling food with the date you opened it is a good way to track freshness. When cleaning, keep rooms well-ventilated and don't mix products.

Regarding food, you can engage in a different way by concentrating on textures and colors. Adding chili flakes, strong spices, or smoky flavors can help enhance the experience. If living with parosmia, you can keep a list of unpleasant triggers and share them with friends and family. You can also break down foods to see which specific ingredients are unpleasant.

Finally, there is research into smell training following a virus or brain injury, which may help with recovery. If your sense of smell or taste is affected, go to your GP and ask for a referral to an ENT (Ear, Nose, and Throat) specialist. Our charity offers peer support groups, online sessions, information sheets, and a support service to help guide you through these challenges.