What are reasons for hallucinating if your are not physically ill, and don't really think you have serious mental illness and stuff?

Dehydration

What drugs were you taking?

Just the same. DO see a doctor. You shouldn’t be having them.

Yeah, being dehydrated and malnourished in general could do it. Typically, healthy people don’t hallucinate. It’d be a good idea to see a doctor.

Staying awake for too long can also be a cause. But not sleeping isn’t good, either.

Lack of sleep.

Apparently, if you stay awake for more than 36 hours or so, your body may spontaneously enter REM sleep (the sleep phase in which we dream). Never happened to me, though.

Welcome to the collective. That sounds scary. Did the once or twice occur over your lifetime or within a few months?

It is quite possibly not serious, but the doctor visit is a great idea to rule out more serious possibilities (such as a brain tumor—I am really not trying to scare you, but you do need to get checked out.).

From healthcares.net

Electrical or neurochemical activity in the brain such as the onset of an epileptic attack
Meditation and/or sensory deprivation
Sleep deprivation and/or exhaustion
Lesions or injuries to the brain
Stress
Drugs

Or any one of hundreds of medical reasons. See you doctor for a complete exam, and discuss your concerns.

what do you see/hear?

this hasnt happened for a while so i was just wondering about it, you know was a while ago and everything…
but last time i saw first of all a big black smudgy thing, and then it turned into this guy in a red jumper getting on to a train/ bus over and over again… for like half an hour… ha… and there was one of those colour wheel things that has all contrasting colours etc etc around it…

anyway being the paranoid person i am i was completley panicking =P

The type of migraines I get can make me see things that aren’t there, and so did the London flu. However, I suggest you talk to your doctor about it, especially if it happens again.

There are various ordinary chemicals that can cause one to hallucinate. Caffeine is one. Hallucinations are not all that uncommon, and are not always caused by something bad. Sometimes it is just a trick of the light, being tired, or your eyes playing tricks on you. If it is freaking you out, talk to a physician.

If you were not doing drugs then something not right was going on in your brain. Only a doctor can really figure it out with tests. Pleas see one soon. It could be as simple as dehydration or as serious as a brain tumor. It should not be ignored.