Changes in perception and hallucinations in dementia

Understanding changes in behaviour in dementia

Print copy below
The content below is reflective of our leaflet.

Why do changes in perception occur?

We understand the world through our senses. There are five senses: hearing, sight, smell, taste and touch. These senses collect information and send it to the brain, which uses it to make sense of the world around us.

For some people living with dementia, their brain misinterprets the information from their senses. This is called ‘changes in perception’, and leads to them misunderstanding the world around them, or, in more rare instances, the person having hallucinations.

Changes in perception can also happen because of physical changes in the brain or the sensory organs, such as our eyes or ears. The most common example of this, is someone’s vision or hearing getting worse as they get older.

In this leaflet, we will look at what exactly we mean by changes in perception and hallucinations, as well as suggesting why these things might be happening. Lastly, we will suggest some ways to prevent or manage the type of misperceptions that can occur in people living with dementia.

What are hallucinations?

Hallucinations happen when a person’s brain misunderstands the information it is receiving from their senses, leading to them experiencing something that is not really happening. Hallucinations may involve any of the senses, but the most common are visual and auditory hallucinations: the person sees or hears something that is not there. Common examples of hallucinations include hearing voices, or seeing a person in front of them who isn’t actually there.

Who does it affect?

Changes in perception and less commonly, hallucinations, can affect anyone who has physical changes to either their sensory organs, or their brain – or both. This means that it can affect people who have sight or hearing problems, delirium, an infection, side effects or adverse effects from taking medication, or the over-use of alcohol.

Changes in perception are more common in people with dementia as they may experience these physical changes to their sensory organs, as well as experiencing changes in the brain. People who are diagnosed with dementia with Lewy bodies are more likely to have visual hallucinations than people with any other form of dementia, due to the particular changes in the brain that take place with this kind of dementia.

Changes in perception and hallucinations in dementia

Order hard copies of our information leaflets

How can I recognise when a person with dementia is experiencing difficulties with their perception?

It can be difficult to know when a person with a diagnosis of dementia is experiencing perceptual difficulties or hallucinations. Signs that this might be happening include:

  • saying or doing things that suggest they see or hear things that you can’t
  • bumping into things or frequent trips and falls, as though they are struggling to see the objects around them
  • not recognising where they are
  • displaying changes in behaviour that may indicate fear or distress
  • becoming more socially isolated
  • reacting to, or looking startled by, things that you can’t see
  • muttering under their breath, or speaking as if in answer to something you cannot hear
  • plucking or picking at their skin as if they itch

Practical tips on preventing perceptual difficulties and hallucinations

Ways to avoid visual misperceptions and hallucinations

  • Take the person for regular eyesight tests
  • If they wear glasses, make sure they’re clean
  • Cover mirrors or turn them around to face the wall. People with dementia can misinterpret reflections as other people in the house
  • Move other objects that could be mistaken for a person; for example, coat stands, dressing gowns or coats hung on doors
  • Prevent reflections from windows with blinds or curtains
  • Avoid busy patterns on carpets or tiles, and, if possible, try to avoid changes in the levels of the floor, such as from thick carpet to bare floor, which might be difficult for a person with dementia to see
  • Make sure rooms are well lit
  • Use contrasting colours to help the person with dementia; for instance, bright, block colour plates help food stand out; brightly coloured towels are easier to see against the wall; a vivid coloured toilet seat is easier to see against the backdrop of the bathroom

Ways to avoid auditory (hearing) misperceptions and hallucinations

  • Take the person for regular hearing tests
  • If they wear a hearing aid, make sure it’s cleaned and maintained, and the battery is checked regularly
  • Speak slowly and calmly to the person
  • Face them when speaking
  • Turn off background noise such as the TV and radio when speaking to them

Ways to avoid taste misperceptions and hallucinations

  • Take the person for regular dental check-ups. Tooth decay or gum disease can create a bad taste in the mouth, which people with dementia can misperceive as something wrong with their food
  • Make sure the person has a daily mouth care routine
  • Check the person’s dentures, teeth and mouth for signs of infection or damage and ask whether they have any discomfort

Ways to avoid sense of touch misperceptions and hallucinations

  • Look for excessive itching or plucking at the skin
  • Find out whether there has been a change in medication; itching might be a side effect
  • Check if there has been a change in washing detergent or fabric conditioner, in case of allergic reaction or skin sensitivity
  • Assess whether the person is too hot or cold
  • Determine whether the person has an allergy to something else.
  • Check if their clothing is causing discomfort

Ways to avoid sense of smell misperceptions and hallucinations

  • Investigate if anything in the house is causing a bad smell; for example, the bin, food that is off, animal waste etc. People with dementia can misperceive bad smells as something worse, for example, a gas leak
  • Encourage the person to follow a hygiene routine, with assistance if necessary

Tips for managing perceptual difficulties and hallucinations as they happen

  • Ask the person what is the matter. Listen carefully to the response and if possible, see if you can deal with the source of their distress
  • Talk in a reassuring, slow, soothing way and explain what is happening but try not to contradict the person, as this may increase their distress
  • Check they are wearing the correct glasses, and/or their hearing aid is working and has charged batteries
  • Use distraction techniques. Suggest you both go into a different room; take them to the kitchen to make a drink; offer them a biscuit; turn some music on; or go out for a walk
  • Hold the person’s hand or sit close to them and stroke their arm
  • Check for possible physical reasons for their distress. Could they have an infection, or be dehydrated or experiencing constipation? See your GP if in any doubt.

Where can I get help and support?

If the person is having episodes of distress which become more regular, or worsen, make an appointment with the GP, so they can rectify or rule out any potentially treatable causes.

The GP will want to know if anything triggers the changes in their behaviour; what the signs and symptoms are; what time of the day the behaviour occurred; for how long; and what, if anything, helps to reduce or stop the behaviour. Try to take this information with you if possible.

The GP should have the person’s medical history and diagnosis available but, if not, some brief notes on this and any changes to medication would be useful.

Sources of support

Dementia UK leaflet on Tips for better communication:

Dementia UK Practical guide to getting the best out of GP
and other health appointments:

Dementia UK leaflet on Making the home safe and comfortable for a person with dementia:

Dementia UK resource on Sources of support for families
and people with dementia: