A hallucination is perceiving something that isn’t there: hearing a sound with no source, seeing something no one else can see, or feeling a sensation on your skin when nothing is touching you. The key distinction is that hallucinations feel completely real in the moment, which is exactly what makes them so hard to identify on your own. If you’re questioning whether what you experienced was real, that self-awareness is actually a useful starting point.
What a Hallucination Actually Is
A hallucination is a perception your brain generates without any external trigger. This is different from an illusion, which is a misinterpretation of something that does exist. Hearing the wind blow and mistaking it for a bird chirping is an illusion. Hearing a bird chirping when it’s completely silent outside is a hallucination. It’s also different from a delusion, which is a false belief rather than a false sensory experience. All three can feel equally convincing, but they involve different processes in the brain.
Hallucinations can involve any of your senses. Auditory hallucinations, like hearing voices or sounds, are the most common type overall. Visual hallucinations involve seeing people, shapes, patterns, or flashes of light that aren’t there. Tactile hallucinations create the feeling of being touched, or of something crawling on or under your skin. Less common are olfactory hallucinations (smelling something with no source) and gustatory hallucinations (tasting something when your mouth is empty).
Signs You Might Be Hallucinating
The simplest reality check is one that mental health professionals actually recommend: ask someone you trust whether they can see, hear, or feel the same thing you do. Making a friend or loved one your “reality tester” gives you an external reference point when your own senses feel unreliable. If you’re alone, try using your phone camera to take a photo or video of what you think you see, or record audio of what you think you hear. If the recording captures nothing, that’s meaningful information.
There are also patterns worth paying attention to. Ask yourself:
- Does the experience have no clear source? You hear a voice but no one is in the room. You smell smoke but nothing is burning. You feel insects on your arm but see nothing there.
- Does anyone else notice it? If other people in the same space don’t react to something vivid and obvious, that’s a strong signal.
- Does it happen only in specific circumstances? Only when you’re extremely tired, only at home, only during periods of high stress. Context can point to the cause.
- Does it feel “too real” or strangely vivid? Some hallucinations have an intensity that feels different from normal perception, though not always.
The tricky part is that many hallucinations are completely convincing while they’re happening. You may only recognize one in hindsight, when the experience stops making sense or when someone else tells you nothing was there. That delay is normal and doesn’t mean something is seriously wrong with you.
Common and Harmless Causes
Not all hallucinations signal a psychiatric condition. Some are ordinary experiences that most people have at some point.
Sleep-related hallucinations are extremely common. Hallucinations that occur as you’re falling asleep (called hypnagogic) affect an estimated 25 to 38 percent of the general population over a lifetime. Hallucinations that happen as you’re waking up (hypnopompic) affect 6 to 13 percent. These can involve vivid images, voices, or the sensation of a presence in the room. They typically last only seconds and happen in that gray zone between sleep and wakefulness. If your experience only happens at the edges of sleep, this is the most likely explanation.
Sleep deprivation is another powerful trigger. After just 24 hours without sleep, research shows that people can begin to hallucinate. After 72 hours, perception of reality can become severely distorted, resembling acute psychosis, with complex hallucinations, delusions, and disordered thinking. Even moderate, chronic sleep loss (consistently getting far less sleep than you need) can make your brain generate false perceptions. If you’ve been sleeping poorly, that alone could explain what you’re experiencing.
High fever, dehydration, extreme stress, grief, and substance use (including alcohol withdrawal) can all produce hallucinations in otherwise healthy people. Even caffeine in very high doses has been linked to auditory hallucinations in some studies.
Environmental Causes Worth Ruling Out
One cause that’s easy to miss and genuinely dangerous: carbon monoxide exposure. At lower levels, carbon monoxide leaks can cause headaches, confusion, blurred vision, hallucinations, and feelings of dread. There are documented cases of people believing their homes were haunted when the actual cause was a CO leak. If your symptoms happen only inside your home, get worse during heating season, or if other household members or pets are also feeling unwell, get a carbon monoxide detector immediately and leave the house if you suspect a leak.
Medical and Psychiatric Conditions
When hallucinations are persistent, recurring, or severe, they can be a symptom of an underlying condition. Schizophrenia is the mental health condition most strongly associated with hallucinations, particularly auditory ones like hearing voices that comment on your behavior or speak to you directly. Bipolar disorder can also cause hallucinations during severe manic or depressive episodes. Major depression with psychotic features involves hallucinations or delusions alongside deep depression.
Several neurological conditions cause hallucinations too. About 20 to 40 percent of people with Parkinson’s disease experience hallucinations or delusions, sometimes as a side effect of their medications. Around 13 percent of people with Alzheimer’s disease have hallucinations caused by changes in the brain. Lewy body dementia, which involves the buildup of abnormal protein clumps that damage nerve cells, commonly causes visual hallucinations. People with temporal lobe epilepsy most often experience olfactory hallucinations, like smelling something that isn’t there.
There’s also Charles Bonnet syndrome, which causes visual hallucinations in people whose eyesight is deteriorating. The brain essentially “fills in” visual information that the eyes can no longer provide. People with this condition often see patterns, faces, or figures, and they typically know these aren’t real. It involves only vision, not other senses.
People with narcolepsy frequently experience vivid hallucinations at sleep transitions, which can be harder to distinguish from the common hypnagogic type because they occur in the same context but tend to be more intense and frequent.
How to Ground Yourself in the Moment
If you’re experiencing something you think might not be real, grounding techniques can help you reconnect with your actual surroundings. The core idea is to engage your senses deliberately with things you know are real.
Feel the ground under your feet. Touch a wall or pick up a small object and focus on its texture, weight, and temperature. Have something to eat or drink and pay attention to the taste. Take a warm bath and notice the sensation of the water. These actions give your brain concrete, verifiable sensory input to compete with whatever it may be generating on its own.
Deep breathing and meditation can also help by slowing your thoughts and pulling your attention to the present moment. Physical movement (stretching, walking, exercise) puts you back in touch with your body. These aren’t cures, but they can reduce the intensity of an episode and help you regain a sense of control.
Longer term, sleep is one of the most protective factors. Sleep deprivation makes it nearly impossible to stay grounded in reality, and keeping a consistent sleep schedule is one of the most effective things you can do if you’re prone to perceptual disturbances. Be mindful of substance use as well, since alcohol, cannabis, stimulants, and even some prescription medications can trigger or worsen hallucinations.
When Hallucinations Become Urgent
Most hallucinations are not emergencies. But certain types require immediate attention. If you hear a voice telling you to hurt yourself or someone else, that’s called a command hallucination, and it needs professional evaluation right away. The same applies if hallucinations are accompanied by severe confusion (you don’t know where you are, what day it is, or who you are), if you feel compelled to act on what you’re perceiving, or if you feel a sense of paranoia that others are trying to harm you.
If someone near you appears to be acting on a hallucination or delusion and there’s any risk of harm, calling emergency services is the right step. Threats or warnings from someone experiencing psychosis should always be taken seriously, even if their perception of reality is clearly distorted.
For non-urgent but recurring hallucinations, the screening questions that mental health professionals use are straightforward: “Do you ever hear things that other people cannot hear, such as noises, or the voices of other people whispering or talking?” and “Do you ever have visions or see things that other people cannot see?” If your honest answer to either is yes and it’s happening regularly, that’s enough reason to bring it up with a doctor or mental health professional. It doesn’t automatically mean a serious diagnosis. It means the experience deserves a closer look.