The terms sore throat, strep throat, and tonsillitis are often used interchangeably, but they don't necessarily mean the same thing.

Tonsillitis refers to tonsils that are inflamed. When your child has a sore throat or strep throat, the tonsils may be inflamed or the inflammation may affect the surrounding part of the throat but not the tonsils. Infectious mononucleosis also can produce a sore throat, often with marked tonsillitis.

In infants, toddlers, and preschoolers, the most frequent cause of sore throats is a viral infection. No specific treatment is required when a virus is responsible, and your child should get better over a three- to five-day period. Often, children who have sore throats due to viruses also have a cold at the same time. They may develop a mild fever, too, but they generally aren't very sick.

One particular virus (called Coxsackie), seen most often during the summer and fall, may cause the child to have a somewhat higher fever, more difficulty swallowing, and a sicker overall feeling. If your child has a Coxsackie infection, she also may have one or more blisters in her throat, which your pediatrician will look for during the examination.

Strep throat is caused by a bacterium called Streptococcus pyogenes. To some extent, the symptoms of strep throat may depend on the child's age. Infants may have only a low fever and a thickened, bloody nasal discharge. Toddlers (ages one to three) also may have a thickened, bloody nasal discharge with a fever. Such children are usually quite cranky and have no appetite and often swollen glands in the neck. Children over three years of age with strep are often more ill; they may have an extremely painful throat, fever over 102 degrees Fahrenheit (38.9 degrees Celsius), swollen glands in the neck, and pus on the tonsils. It's important to be able to distinguish a strep throat from a viral sore throat because strep infections must be treated with antibiotics.

Any time your child has a sore throat that persists (one that doesn't go away after her first drink of juice in the morning), whether or not it is accompanied by fever, headache, stomachache, or extreme fatigue, you should call your pediatrician. That call should be made even more urgently if your child seems extremely ill, or if he has difficulty breathing or extreme trouble swallowing (causing him to drool). This may indicate a more serious infection.

The pediatrician will examine your child and may perform a throat culture to determine the nature of the infection. To do this, he will touch the back of your child's throat and tonsils with a cotton-tipped applicator and then smear the tip onto a special culture dish that allows the strep bacteria to grow if they are present. The culture dish usually is examined 24 hours later for the presence of the bacteria.

Most pediatric offices now are doing quick-result strep tests that provide findings within minutes. However, when these tests are negative, their results still need to be confirmed with a 24-hour culture. If the result of the culture is still negative, the infection usually is presumed to be due to a virus. In that case, antibiotics will not help and should not be prescribed.

If your child's strep test is positive, your pediatrician will prescribe an antibiotic to be taken by mouth or by injection. If your child is given the oral medication, it's very important that she take it for the full 10-day course, as prescribed, even if the symptoms get better or go away.