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Asked by: Maclaine Farrell
School:St. James Middle School
Teacher:Mrs. Walter

Sing, dance, tennis, soccer, swim, ski, reading

Career Interest:News Reporter


Answered by: Leann Lesperance
Title:Assistant professor, Binghamton University
About Scientist:

Research area: Complex systems, chronic illness, healthcare quality.

PhD school: Harvard-MIT

Husband, Drew, daughters Teresa (7) and Catherine (5)

Singing, nutrition/fitness.


Date: 04-02-2008

Question: Why do you hallucinate when you don't eat or drink or if you're too hot?


When someone hallucinates, it means the person sees or hears something that is not really there. In other words, the person's mind plays tricks on him. This can happen when the nerve cells in the brain send signals to the eyes or ears for the wrong reason.

In the movies, hallucinations most often happen when an actor is lost in the desert for a few days. He wanders around, desperately looking for water and finally thinks he sees some. He musters up all his strength and struggles toward the water, only to find that there is no water, only more sand.

In real life, hallucinations sometimes can happen when a person doesn't drink enough and gets dehydrated. All of the cells in our body need water to work properly. If the brain doesn't have enough water, it cannot work properly and may send incorrect signals, which could cause hallucination. If it is very hot outside, your body will lose water faster than normal (for example, from sweating) and it is even easier to get dehydrated. Remember to drink plenty of water when you are outside in hot weather, especially if you are playing hard!

Hallucinations also can happen when you don't eat for long periods of time, causing the sugar (glucose) levels in your blood to get low. When blood sugar is low, your brain will not do its best work. Again, it may send some error messages to the eyes and ears. That is one of the reasons that it is so important to eat a healthy breakfast and lunch every day!

Some people hallucinate a little when they are falling asleep, especially if they are extremely tired. Perhaps you have felt as though you were falling and startled yourself awake. Other causes of hallucinations include fevers (especially in young children and older people), medications, medical conditions such as migraine headaches, and mental illness.

Hallucinations can mean that something is wrong so they always should be reported to a doctor as soon as possible.

Ask a Scientist appears Thursdays. Questions are answered by faculty at Binghamton University.  Teachers in the greater Binghamton area who wish to participate in the program are asked to write to Ask A Scientist, c/o Binghamton University, Office of Communications and Marketing, PO Box 6000, Binghamton, NY 13902-6000 or e-mail Check out the Ask a Scientist Web site at To submit a question, download the submission form(.pdf, 460kb).

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Last Updated: 6/22/10