Family Health Guide

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Allergies: Causes

Allergies are the result of an over-reaction in the immune system to substances that are normally harmless. When children who are allergic come into contact with these substances, called allergens—such as dust or pollen, peanuts or shellfish—their bodies produce an antibody to it. That sets off a process that triggers the allergic response.  
For example, if your child is allergic to pollen, his immune system identifies pollen as an invader and over-reacts by producing antibodies called Immunoglobulin E (IgE). These antibodies trigger the release of chemicals, such as histamine, which set the allergic reaction in motion. The result: itching, stuffiness, and and/or swelling in the nose, lungs, throat, sinuses, ears, lining of the stomach or on the skin. Although allergies do not cause asthma, they can trigger it. In fact, allergic asthma is the most common type in the United States.     

Although any food can trigger an allergic reaction, certain ones top the list. These include:

  • Peanuts
  • Tree nuts (such as walnuts, pistachios, pecans and cashews)  
  • Shellfish (such as shrimp and lobster)
  • Fish (such as tuna, salmon and cod)
  • Cow’s milk
  • Wheat
  • Soy
  • Eggs

The good news for some kids is that food allergies can be outgrown. Up to 90 percent of egg, milk, wheat and soy allergies go away by age 5 years. But others are likely to continue as children grow up. Only about 1 in 5 young kids outgrow their allergy to peanuts and even fewer outgrow their allergies to tree nuts or seafood. Your pediatrician or allergist can test your child over time to see if food allergies are going away or getting worse.

Seasonal allergies are brought on by various types of pollen or mold. If your child is 4 or older and sniffles and sputters throughout the first few weeks of spring, an allergy to a specific pollen is probably to blame.  Children typically have a “hay fever” season that depends on where they live.  The season tends to start in the spring and continue until the fall. Symptoms rise along with increasing levels of pollen from ragweed, grass, weeds, and trees as well as mold spores.   

But the indoor environment can just as easily be the culprit. Some children are bothered by dust mites, microscopic spider-like creatures that nestle where there is lots of food for them—flakes of human skin! Upholstered furniture, carpets, mattresses, stuffed animals, pillows and blankets are prime breeding grounds. Other kids react to molds and pet dander. Cats and dogs are tops on the list, but your child can also be allergic to guinea pigs, gerbils, rabbits and other pets.