Dementia is a condition that changes the way a person’s brain works, and one of the earliest and most noticeable changes is how someone reacts to familiar scents. Many people with dementia find that smells they once recognized or enjoyed no longer feel the same, or sometimes they do not recognize them at all. This happens because dementia affects the parts of the brain that process smell, and as the disease progresses, these changes can become more obvious and more troubling for both the person and their loved ones.
The sense of smell, also called olfaction, is closely tied to memory and emotion. When you smell something, like fresh bread or a favorite perfume, your brain connects that scent to past experiences and feelings. This is why certain smells can instantly bring back memories or make you feel happy or sad. But in dementia, especially in Alzheimer’s disease, the brain’s ability to make these connections starts to break down. The part of the brain that handles smell, called the olfactory bulb, is one of the first areas to be affected by the disease. Researchers have found that the brain’s immune cells begin to dismantle the nerve connections between the olfactory bulb and other parts of the brain, which means that the signals from smells do not get through as clearly as they used to [3].
This breakdown means that people with dementia may not recognize familiar scents, or they may react to them in unexpected ways. For example, someone who used to love the smell of coffee might suddenly find it unpleasant or confusing. Sometimes, they might not notice the smell at all. This is not just about losing the ability to smell, but also about losing the emotional and memory connections that go along with it. The brain is no longer able to link the scent to the right memories or feelings, so the experience of smelling something familiar becomes different or even meaningless [3].
Studies have shown that changes in how people react to familiar scents can be an early warning sign of dementia. In fact, problems with smell are often noticed years before other symptoms like memory loss or confusion become obvious. This is why doctors sometimes use smell tests as part of dementia screening. If someone cannot identify common scents like lemon, chocolate, or roses, it could be a sign that something is wrong with their brain, even if they do not have other symptoms yet [3].
The way dementia affects reactions to familiar scents is not just about losing the ability to recognize them. Sometimes, people with dementia may have strange or even distressing reactions to smells. They might become anxious or upset when they smell something that used to be comforting, or they might not react at all to something that should be strong or noticeable. This can be confusing and upsetting for both the person with dementia and their caregivers. It is important to understand that these changes are not the person’s fault, but are a result of the disease affecting their brain [1].
Another thing that can happen is that people with dementia may start to experience phantom smells, also called olfactory hallucinations. This means they smell something that is not really there, like burning or something rotten. These hallucinations can be very real to the person and can cause fear or confusion. They are more common in certain types of dementia, like Lewy body dementia, but can happen in other forms as well. The reason for these hallucinations is not fully understood, but it is thought to be related to the way the brain is processing sensory information as the disease progresses [1].
The loss of smell and changes in how familiar scents are experienced can also affect a person’s quality of life. Smell is linked to appetite and enjoyment of food, so when someone cannot recognize or enjoy familiar scents, they may lose interest in eating. This can lead to weight loss and other health problems. Smell is also important for safety, as it helps people notice things like smoke or spoiled food. When this ability is lost, it can put the person at risk [2].
Researchers are working to understand more about how dementia affects the sense of smell and how this knowledge can be used to help people with the disease. Some studies are looking at ways to use virtual reality and other technologies to help people with dementia “experience” lost smells again, by helping their brains expect and imagine familiar scents. This could help improve their quality of life and reduce some of the distress caused by sensory loss. There is also hope that understanding how smell is affected by dementia could lead to new treatments or ways to slow down the progression of the disease [1].
In addition to medical research, there is growing interest in how smell can be used in care settings for people with dementia. Some care homes and hospitals are using familiar scents, like lavender or baking bread, to help create a calming environment and trigger positive memories. This is based on the idea that even if a person cannot recognize a scent, the emotional and memory connections may still be there, and the scent can help them feel more relaxed or happy [4].
Overall, dementia has a big impact on how people react to familiar scents. The changes are not just about losing the ability to smell, but about losing the connections between smells, memories, and emotions. These changes can be an early sign of dementia, and they can affect a person’s quality of life in many ways. Understanding how dementia affects the sense of smell is important for both medical care and everyday support for people with the disease.
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC12644582/
[2] https://jamanetwork.com/collections/5800/olfaction-and-taste
[3] https://www.sciencedaily.com/news/mind_brain/dementia/
[4] https://www.brown.edu/news/2025-11-24/chanelle-dupuis-smell-studies/
