The Walt Disney movie "Snow White" is 50 years old this year. For generations, kids have been enjoying Snow White's adventures with the Seven Dwarfs -- and watching as the beautiful girl eats a poisoned apple sent to her by the wicked Queen. She takes a bite of the apple, falls down and seems to be dead. Luckily for Snow White, Prince Charming comes along and wakes her up, and they live happily ever after.

In real life, recovering from a poisoning isn't always that easy. Poison is a serious danger to many children. It's a good idea to know how to recognize poison and to know what to do if an accidental poisoning happens.

According to the American Association of Poison Control Centers, more than 3 million children 5 and younger were victims of accidental poisonings in the United States last year. Most of these children are treated in time and suffer no serious damage. But about 100 kids die from poisonings every year. Very young children, like toddlers who don't know when something is dangerous, are most at risk. One of their favorite ways to explore new things is to taste them -- and that can mean trouble.

You're old enough to know that you shouldn't eat a whole bottle of children's aspirin or chew on some nice-looking berries on an unfamiliar bush out in the woods. But little kids aren't.

Even so, older kids sometimes eat or drink dangerous things or take pills that are too strong for them. Emergency rooms often have to treat kids who have decided to try one of their parents' or grandparents' medicines -- with very serious results. There are hundreds of thousands of substances that can be poisonous to human beings.

A whole branch of science called toxicology is devoted to understanding how these substances work. Some plants are poisonous if you eat them. Many common cleaning materials are very dangerous. Nail-polish remover, laundry bleach and even some shampoos can be harmful if swallowed. Paints, paint thinners, garden fertilizer and other things used around the house can be poisonous, too.

Some poisons are harmful because they cause burning inside the body. These poisons are called caustics. Drain cleaners are caustics. Other poisons affect the heart, making it beat too fast or too slow. Others depress, or slow down, the part of the brain that regulates breathing. Still others cause paralysis or make people have violent muscle spasms called convulsions. Poison is really nasty stuff.

There are several hundred poison control centers all across the country, where well-trained people answer telephone hotlines. These people keep up to date on which substances are poisons and what to do if someone eats or drinks them. Regional poison control centers report that they get between 100 and 200 calls each day. Sometimes, the hotline workers just give people advice. At other times, they have to cope with emergencies. They can tell you if something a child ate is poisonous and what the best way to deal with the problem is. They can tell you whether you need to rush the victim to the emergency room.

Experts say that the best way to deal with the poison problem is through prevention. Since drug manufacturers started making child-proof caps, for example, the number of serious poisonings of very young kids has gone down. Drug companies also now sell children's pain-relief medicines in small containers, so that even if someone does manage to eat a whole bottle's worth, no serious harm will come of it.

Even with these precautions, though, it's still a good idea to keep pill containers of any kind locked away from little kids. If there are small children around the house, it's a good idea to keep anything dangerous in a cupboard beyond their reach. It may be inconvenient to have to reach for the cleanser every time you want to clean the sink. But it's not as inconvenient -- or scary -- as a trip to the emergency room with a sick child! If you are ever in a situation where you think someone has eaten poison, don't try to treat the problem yourself. Call a poison control center immediately, and get professional help.

As soon as you finish reading this column, why don't you go look up Poison Control Center in your phone book, and make a poster with the number on it to hang by the phone? That way, the number will be close by if you need it. Tips for Parents

In addition to such common-sense measures as keeping toxic substances out of reach of your kids, the American Academy of Pediatrics recommends that parents keep a small amount of syrup of ipecac on hand in case of a poisoning emergency. However, the AAP cautions, NEVER give the syrup before consulting a poison control center. While some poisons should be expelled from the body by vomiting, others -- like caustics -- will do even more damage if vomiting is induced. The first step to take if you suspect poisoning is to try to determine what your child took, and call your regional poison control center. Post the number in a prominent place near every phone in your house. In the District, call the Poison Center at Georgetown University Hospital at 625-3333. The National Capital Poison Center serves the Maryland area. Its numbers are 1-800-494-2414 or (301) 528-7701. In Northern Virginia, call 379-3070 in Alexandria, or check your phone book for the center nearest you.

Catherine O'Neill is a free-lance children's writer based in Baltimore.