Common infections
The most common infections are viral respiratory tract infections—colds. The average young child may get up to 12 colds a year. Typically, cold symptoms last five to 10 days. If a child gets 12 colds a year, each lasting about 10 days, it may seem like they are sick half the time—because they are! These infections, however, are not a cause for concern. Colds are a result of the close contact young children have with other infected children and the fact that their immune systems are relatively immature. Once a child's immune system learns the faces of many of the germs that cause such colds, the child will get infected less frequently.

Another infection, strep throat, is also a "social disease" that children and adults catch because they are in close contact with infected individuals. Although we don't completely understand why some people get strep throat frequently, we know that recurrent strep throat is rarely an indicator of immunodeficiency.

Many people confuse allergic rhinitis, or "hay fever"—which causes stuffiness, nasal itch and a runny nose that lasts for weeks, but is not an infection—with a cold or sinus infection. Your allergist/immunologist can help you differentiate allergies from infection. Once the possibility of allergy is eliminated, your allergist will consider which infections reflect a high exposure to other people with infection, and which infections are warning signals of an immune system problem called immunodeficiency .

   Immunodeficiency signs
People with immunodeficiency get the same kinds of infections that other people get—ear infections, sinusitis and pneumonia. The difference is that their infections occur more frequently, are often more severe, and have a greater risk of complications. Patients with immunodeficiency are more likely than other people to develop infections inside the body, for example, in the bones, joints, liver, heart or brain.

In most cases, the frequency of infection is the most important issue, but sometimes a single infection with an unusual germ is enough to trigger the need for the doctor to perform a thorough immunologic evaluation of the patient.

So, how many infections are too many? Allergists/immunologists often use the frequency of

antibiotic use to mark the occurrence of frequent infections. Older children and adults with healthy immune systems seldom require antibiotic treatment. However, for the reasons mentioned above, many younger children receive several courses of antibiotic therapy each year.

General guidelines for determining if a patient is experiencing too many infections are:

• the need for more than four courses of antibiotic treatment per year in adults;
• the occurrence of more than eight new ear infections in one year;
• the development of pneumonia twice in one year;
• the occurrence of more than four episodes of bacterial sinusitis in one year; or
• the need for intravenous antibiotics to treat infection.

If a patient has two or more of the conditions noted above, or if a patient with recurrent respiratory tract infections has one of those conditions, the need for an immunodeficiency evaluation may be indicated. Although infants are more likely to catch respiratory tract infections than older patients, monitoring infection in infants and small children is especially important because the most serious immunodeficiencies usually become apparent during the first years of life. Persistent fungal infection of the mouth or skin, prolonged diarrhea or persistent cough are all signs that suggest a doctor should further examine the patient. If a primary care or family physician believes that a patient's infections exceed the normal range, the doctor should refer the patient to an immunology specialist.

The most common forms of immunodeficiency are caused by defects in the patient's ability to produce blood proteins called antibodies . Antibodies are proteins that attach to germs and help the body eliminate them. Simple blood tests can measure the number of antibodies a patient is producing. To fully evaluate your antibody health, your physician may want to measure a specific antibody response by giving you diptheria, tetanus and pneumococcal (pneumonia) vaccines and performing a blood test three to four weeks later. Skin tests or more specialized blood tests can diagnose other forms of immunodeficiency. Allergy skin tests are sometimes done because allergies often contribute to infection susceptibility, and many patients with immunodeficiency also suffer from allergies.

   Treatment of recurrent infections
Although it is not possible to completely prevent allergies and asthma in young children with the knowledge we currently have, genetic and cellular engineering promise hope for such absolute prevention in the future. In the meantime, parents with allergies or asthma can make the recommended environmental changes and use the preventative strategies discussed to help reduce or delay the occurrence of allergies and asthma in their children.