If the sight of a big, red, painted smile and abnormally large shoes gets your palms sweating and heart thumping, don't feel alone. A recent study by the University of Sheffield determined clowns are scary.

One place you won't find clowns is on the walls of the Medical College of Georgia's Children's Medical Center, which is in accordance with the study's recommendations.

Though clowns and other costumed characters come in to visit the children from time to time, the staff serves as bouncers for the visit -- if a child looks scared, the character's out of there, said Kim Allen, MCG's manager of child life.

Fear is a universal emotion, and age and experience determine what you're scared of.

It's an unpleasant emotion a person feels when in a dangerous situation, said Terry Miller, a mental health counselor for children and adolescents at the Aiken-Barnwell Health Center's Hartzog Center in North Augusta. Sweaty palms, "butterflies" in your stomach and trouble with speaking can be a physiological result.

It's unpleasant, but sometimes a little fear can be good for you.

Some fears, such as a fear of dogs, can keep a child from playing with a dog that might be dangerous, said Dr. Sandra Sexson, a professor and the chief of the Department of Child, Adolescent and Family Psychiatry at the Medical College of Georgia.

"A little fear probably isn't a bad thing," she said.

Dr. Patrick Boudewyns, a professor of psychiatry and behavioral psychologist at MCG, said a child's specific fears either develop into more generalized anxieties as an adult or reach extinction through time and life experience.

Fears of children are often related to separation anxiety from their parents, Dr. Sexson said.

Augustan Susan Plantamura's oldest child, Natalie, went through the stranger anxiety phase, but her son, Nicholas, 3, hasn't had any fears.

"We went through the monster fear at 4," Mrs. Plantamura said, but since then, 5-year-old Natalie has grown out of it.

Dr. Sexson said such fears aren't a problem unless they last several weeks or months.

"If there's a lot of stress at home, the kids will have more anxieties in general," said Dr. Kerry Ressler, an assistant professor in the Department of Psychiatry and Behavioral Sciences Center for Behavioral Neuroscience and Yerkes Research Center at Emory University in Atlanta.

Some common fears that cross generational lines include fears of heights and planes and social phobias.

Fears developed in adulthood usually stem from a specific incident or experience. For example, if you were involved in a wreck, you might fear driving again, and avoid it.

Fears of snakes or heights were once thought to be part of our genetic memory, but Dr. Ressler said it's more a combination of a predisposition and experience.

A group of primates were found in captivity that weren't afraid of snakes, but after being shown a video in which other monkeys were scared of a rubber snake, the fear was socially transmitted, he said.

That might also explain similar common fears, such as fear of large dogs or bad weather.

Some things aren't scary. The monkeys were shown a video with a flower superimposed over the snake, but they didn't become afraid of flowers, he said.

A fear of being afraid, or a panic disorder, can lead to the "granddaddy of all fears," Dr. Boudewyns said: agoraphobia.

Panic disorders are characterized by sudden panic attacks that come on for no reason. Fear implies a threat, Dr. Boudewyns said, but someone with a panic disorder isn't experiencing a threat when he or she becomes fearful.

"They can't figure out what they're afraid of," he said.

Agoraphobia is when people with a panic disorder avoid certain places because they link the place with a panic attack, since they can't figure out the cause. But eventually, he said, it generalizes to more places.

It's not just clowns that invoke fear in young children.

For Mrs. Plantamura's youngest child, 1-year-old Noelle, "anything in a costume" was terrifying. The family's singing Santa figurine during the holidays scared her so much that it had to be moved.

Dr. Ressler says if you look back into the past of a person who is scared of clowns, you might find a scary clown at the circus or some other way the emotion was learned.

"Almost always you can find that experience," he said.

This fear develops very early in life, usually before language develops, when a child is plopped onto Santa's lap.

Dr. Sexson said a clown's horn or even Santa's "Ho, ho, ho" can scare children at 3 years old.

"They have exaggerated features, or too bright of colors," she said, lending some logic to the clown fear factor.

Dr. Boudewyns said it's all part of the survival instinct.

"They're strange-looking. Children are always reticent about new things," he said.

It's also the separation from the parent, and the fear can linger on into adulthood, making the person feel uncomfortable around clowns or Santa.

Medication can help ease the symptoms for unavoidable situations, but therapy treats the fear, Dr. Ressler said.

There is also virtual reality. The virtual reality therapy isn't a couch potato activity -- it's a fully immersive experience. Dr. Maryrose Gerardi, an assistant professor in the psychiatry department at Emory, is the therapist for a study that is examining the effects of a virtual Iraq on veterans suffering from post-traumatic stress disorder.

This treatment evolved from earlier treatments for a fear of heights, which had a virtual "glass elevator"; a virtual airplane; and a virtual audience for those with social anxieties such as public speaking. A virtual Iraq experience uses a moveable platform and a head-mounted device so users are not only seeing Iraq, but hearing and smelling it as well.

"They may hear a prayer call from a mosque," Dr. Gerardi said, and smell diesel fuel.

It's a "one foot there, one foot here" strategy that allows them to feel safe but still elicits fear.

"Our goal is to not have them avoid the memory," Dr. Gerardi said.

Because of its effectiveness, the therapy requires only six sessions.

The study also is looking at a new medication that might help speed the extinction of fear. The three-part study administers the drug D-Cycloserine to one group; Xanax, an anti-anxiety medication, to another; and a placebo pill to the third group.

But facing your fear is the best bet for your anxiety go the way of the dinosaur, Dr. Ressler said.

"Over time, they learn to be less afraid of it."