Many inhalants have a strong smell. That's why they're called inhalants: Some people inhale the vapors on purpose.

Why would anyone do this? Because the chemicals in these vapors can change the way the brain works, and those changes can make people feel very happy for a short time.

But inhalants can also do harm. Inhalant vapors often contain more than one chemical. Some leave the body quickly, but others are absorbed by fatty tissues in the brain and nervous system. They can stay there for a long time.

One of these fatty tissues is myelin -- a protective cover that surrounds many of the body's nerve cells (neurons). Nerve cells in your brain and spinal cord are sort of like "Command Central" for your body. They send and receive messages that control just about everything you think and do.

If you picture nerve cells as your body's electrical wiring, then think of myelin as the rubber insulation that protects an electrical cord. One problem with inhalant use over the long term is that the chemicals can break down myelin. And if myelin breaks down, nerve cells may not be able to transmit messages.

Inhalants can slow or stop nerve cell activity in some parts of the brain. This might happen in the frontal cortex, the part of the brain that solves complex problems and plans ahead. Or if inhalants get into the brain's cerebellum, which controls movement and coordination, they can make someone move slowly or clumsily.

Studies show that neurons in a part of the brain called the hippocampus can also be damaged by inhalants. The damage occurs because the cells don't get enough oxygen.

Since the hippocampus helps control memory, someone who repeatedly uses inhalants may lose the ability to learn new things, may not recognize familiar things, or may have a hard time keeping track of simple conversations.