Many kids have habits that can be downright annoying. The five most common ones that children develop and parents complain about are:

• nail biting
• thumb sucking
• hair twirling
• nose picking
• breath holding

Although your child's habits may bother or even worry you, relax. In most cases, a habit is just a phase in the normal developmental process and is not cause for alarm.

What's a Habit?

A habit is a pattern of behavior that's repeated, and the person usually isn't even aware of the habit. Although children may be blissfully unaware of their behavior, their parents aren't so lucky.

And if your little one usually has one hand stuffed in the mouth and the other entwined in the hair, your child's habits may bug you twice as much, but it's not surprising: Habits tend to occur in clusters.

A Quick Look at Kids' Habits

Here's the lowdown on the most common habits among children and teens:

Nail Biting

If wet fingers on your child and little slivers of fingernails on the floor are familiar to you, you're not alone. One of the most common childhood habits is nail biting or picking.

Some studies estimate that 30% to 60% of children between the ages of 5 and 10 chew on one or more nails, as do about 20% of adolescents (the habit is less common in preschool children). And, occasionally, a child may also bite his or her toenails.

Both boys and girls appear equally prone to the habit in earlier years; however, as they get older, boys are more likely to be nail biters.

Hair Twirling

If your child is a hair twirler, the odds are that it's your daughter. The majority of children who twist, stroke, or pull their hair are girls.

Hair twirling may appear in early childhood and may be a precursor to hair pulling, either with or without hair loss. But many hair twirlers and pullers stop as they get older. For those who don't, simple behavior modification can help them break the habit. However, for people who start hair pulling as older children or teens, the habit is harder to break and may be a sign of anxiety, depression, or obsessive-compulsive disorder.

Nose Picking

Nose picking appears to be a habit that, although it usually begins in childhood, may actually linger into adulthood. If you find that hard to believe, consider that a 1995 study of adults found that 91% picked their noses on a regular basis - and about 8% of those people reported that they eat what they pick!

Thumb Sucking

The popularity of the thumb as the preferred digit to suck might suggest that it's more flavorful than, say, the index finger. But the preference for thumbs appears to be an accidental choice, resulting from the thumb coming into contact with the mouth during random movements made by an infant.

Some children also suck their fingers, hands, or their entire fists in addition to, or instead of, their thumbs. Most thumb suckers are younger children. In fact, anywhere from a quarter to half of 2- to 4-year-olds suck their thumbs.

Many children suck their thumbs to calm and comfort themselves. But frequent or intense thumb sucking beyond 4 to 6 years of age can cause problems, including dental problems, (such as overbite), thumb or finger infections, and being teased.

Breath Holding

When Shirley Temple used to threaten to "hold my breath till I turn blue" to get her way, movie audiences laughed. But if your 2-year-old tries the same thing, it can be a frightening experience.

However, this relatively common behavior, which usually begins between 6 and 18 months of age and rarely persists beyond 6 to 7 years of age, is more alarming to parents than dangerous for the child.

Breath holding is a reflex event that's typically preceded by crying due to a minor injury, anger, fear, or frustration. In some cases, the child may hold his or her breath long enough to pass out and the child even may have a brief seizure. A seizure as a result of a breath-holding episode is not harmful in itself, unless the child is injured while falling. Speak with your child's doctor for reassurance that even if your child passes out or has a seizure, he or she will not be harmed.

It's important for parents to look at how they respond to the spell and if their fear is reinforcing the behavior. Parents may need to learn how to set consistent limits for their child and to overcome their own fears and anxieties around the breath-holding spells.

What Causes a Habit?

Why do your son's fingers appear to be an extension of his mouth, and why is there always a propeller of hair circling above your daughter's head? Experts admit that they're not always sure what causes a habit, but that it is a learned behavior that usually provides a positive outcome for the child.

Habits may develop as entertainment for a bored child or, more commonly, as a coping mechanism to soothe an anxious one. The next time you see your child biting his or her nails or twirling his or her hair, try to recall if your child has recently had a stressful experience. He or she may be trying to relieve tension just as you would by working out at the gym.

On the other hand, some people engage in habits when they're relaxed, such as before falling to sleep or quietly listening to music.

Other habits may be left over from infancy. In infants, thumb sucking is a common self-comfort behavior that has pleasurable associations with feedings and the end of hunger. The behavior may linger into childhood because of its positive associations.

Or perhaps the explanation for your child's nail biting is in your mirror. Do you bite your nails? Studies suggest that nail biting may have a strong familial or genetic component.

Still, other children will engage in habits to attract attention or as an attempt to manipulate their parents. If kids feel that their parents are ignoring them, they may engage in the annoying habit because they know that it will provoke a reaction from Mom or Dad.

For example, although breath-holding spells are involuntary, a child who doesn't want to go to bed early may learn to have a tantrum to bring on a breath-holding spell that frightens the parents into allowing the little one to stay up longer. Overprotective or anxious parents may inadvertently reinforce this behavior.

Coping With Your Child's Habit

The good news is that most habits disappear. They drive some parents crazy, whereas others are more tolerant. In many cases, if a parent ignores a habit, the behavior will eventually stop because the child no longer needs it or has outgrown it. Many habits, in fact, do disappear by the time a child reaches school age.

But if you think it's time to help your child break a habit, you may want to try the following steps:

• Calmly point out what you don't like about the behavior and why. This approach can be used with children as young as 3 and may help increase your child's awareness of the problem. Say something like, "I don't like it when you bite your nails. It doesn't look nice. Could you try to stop doing that?" Most important, the next time you see your child biting his or her nails or twirling his or her hair, don't scold or lecture. Punishment, ridicule, or criticism could cause the behavior to escalate.
• Involve your child in the process of breaking the habit. If your 5-year-old comes home crying from kindergarten because the other kids made fun of his or her thumb sucking, understand that this is your child's way of asking you for help. Parents can ask their children what they think they could do to stop the habit or if they want to stop the habit.
• Clearly and positively state the alternative behavior you desire. For example, when you catch your child biting his or her nails, instead of saying, "Don't bite your nails," try saying, "Let's wiggle our fingers." This will increase your child's awareness of the habit and may serve as a reminder. To occupy your child's attention, you can also try to give your child something else to do such as helping you in the kitchen or working on a craft. (Using foul-tasting - but safe and nontoxic - substances applied to your child's fingers may help discourage nail biting or thumb sucking, but continually using them diminishes their effectiveness.)
• Reward and praise your child when he or she displays self-control. For example, allow your little girl to use nail polish if she lets her nails grow. Or every time your son refrains from sucking his thumb, reinforce the positive behavior by praising him and giving him a sticker or other small prize.
• Be consistent in rewarding good behavior. If you notice the bad habits but fail to notice good behavior, it will disappear through time. The new, positive habit must be firmly established before the old one will disappear.

For the best success, it's important that your child is also motivated to break his or her habit. And because habits take time to develop, they're also going to take time to be replaced by alternative behavior, so be patient.

When Is a Habit No Longer Just a Habit?

In some instances, a habit may be the result or the cause of a physical or psychological problem. For example, a child who picks his or her nose may be uncomfortable because he or she has actually stuck an object in the nose. And the habits themselves may cause some medical complications, such as:

• nosebleeds in the nose picker
• ingrown or infected nails in the nail biter
• dental problems, such as malocclusion (the failure of the teeth in the upper and lower jaws to meet properly) or thumb or finger infections

A habit may no longer be a simple habit if it negatively affects a child's social relationships or interferes with his or her daily functioning.

An older child who constantly sucks his or her thumb might be experiencing significant stress or anxiety. If kids are the subject of teasing at school or have difficulty talking because they won't take their thumbs out of their mouths, the behavior has progressed beyond a simple habit. A teen who's pulling her hair out may have trichotillomania, a condition that results in obvious hair loss. And habits that are in response to obsessive thoughts may be a sign of obsessive-compulsive disorder.

However, most habits don't cause any significant problems and tend to improve as children get older. If you're concerned about your child's habits, talk with your child's doctor.

Updated and reviewed by: Mary L. Gavin, MD
Date reviewed: January 2005
Originally reviewed by: D'Arcy Lyness, PhD