Allergies 1

 

About Allergies

An allergy is an overreaction of the immune system to a substance that's harmless to most people. But in someone with an allergy, the body's immune system treats the substance (called an allergen) as an invader and reacts inappropriately, resulting in symptoms that can be anywhere from annoying to possibly harmful to the person.
In an attempt to protect the body, the immune system of the allergic person produces antibodies called immunoglobulin E (IgE). Those antibodies then cause mast cells and basophils (allergy cells in the body) to release chemicals, including histamine, into the bloodstream to defend against the allergen "invader."
It's the release of these chemicals that causes allergic reactions, affecting a person's eyes, nose, throat, lungs, skin, or gastrointestinal tract as the body attempts to rid itself of the invading allergen. Future exposure to that same allergen (things like nuts or pollen that you can be allergic to) will trigger this allergic response again. This means every time the person eats that particular food or is exposed to that particular allergen, he or she will have an allergic reaction.

Who Gets Allergies?

The tendency to develop allergies is often hereditary, which means it can be passed down through your genes. However, just because you, your partner, or one of your children might have allergies doesn't mean that all of your kids will definitely get them, too. And someone usually doesn't inherit a particular allergy, just the likelihood of having allergies.
But a few kids have allergies even if no family member is allergic. A child who is allergic to one substance is likely to be allergic to others as well.

Common Food Allergens

The American Academy of Allergy, Asthma, and Immunology estimates that up to 2 million, or 8%, of kids in the United States are affected by food allergies, and that eight foods account for most of those food allergy reactions in kids: eggs, fish, milk, peanuts, shellfish, soy, tree nuts, and wheat.

• Cow's milk (or cow's milk protein). Between 1% and 7.5% of infants are allergic to the proteins found in cow's milk and cow's milk-based formulas. About 80% of formulas on the market are cow's milk-based. Cow's milk protein allergy (also called formula protein allergy) means that the infant (or child or adult) has an abnormal immune system reaction to proteins found in the cow's milk used to make standard baby formulas, cheeses, and other milk products. Milk proteins can also be a hidden ingredient in many prepared foods.
• Eggs. One of the most common food allergies in infants and young children, egg allergy can pose many challenges for parents. Because eggs are used in many of the foods kids eat — and in many cases they're "hidden" ingredients — an egg allergy is hard to diagnose. An egg allergy usually begins when kids are very young, but most outgrow the allergy by age 5. Most kids with an egg allergy are allergic to the proteins in egg whites, but some can't tolerate proteins in the yolk.
• Seafood and shellfish. The proteins in seafood can cause a number of different types of allergic reactions. Seafood allergy is one of the more common adult food allergies and one that you don't always grow out of.
• Peanuts and tree nuts. Peanuts are one of the most severe food allergens, often causing life-threatening reactions. About 1.5 million people in the United States are allergic to peanuts. (Peanuts are not a true nut, but a legume — in the same family as peas and lentils, although people with peanut allergy don’t usually have cross-reactions to other legumes). Half of those allergic to peanuts are also allergic to tree nuts, such as almonds, walnuts, pecans, cashews, and often sunflower and sesame seeds. Like seafood allergy, peanut allergy is one you don't always grow out of.
• Soy. Like peanuts, soybeans are legumes. Soy allergy is more prevalent among babies than older children; about 30% to 40% of infants who are allergic to cow's milk are also allergic to the protein in soy formulas. Soy proteins, such as soya, are often a hidden ingredient in prepared foods.
• Wheat. Wheat proteins are found in many of the foods we eat — some are more obvious than others. As with any allergy, an allergy to wheat can happen in different ways and to different degrees. Although wheat allergy is often confused with celiac disease, there is a difference. Celiac disease is caused by a sensitivity to gluten, which is found in wheat, oat, rye, and barley. It typically develops between 6 months and 2 years of age and the sensitivity causes damage to the small intestine in a different way to the usual allergic reaction.

Other Common Allergens

• Insect stings. For most kids, being stung by an insect means swelling, redness, and itching at the site of the bite. But for those with insect venom allergy, an insect bite can cause more severe symptoms. Although some doctors and parents have believed that most kids eventually outgrow insect venom allergy, a recent study found that insect venom allergies often persist into adulthood. An allergy evaluation is needed if wheezing and other signs of anaphylaxis are present after an insect sting or bite.
• Medicines. Antibiotics — medications used to treat infections — are the most common types of medicines that cause allergic reactions. Many other medicines, including over-the-counter medications, can also cause allergic reactions. If you suspect a medicine allergy, talk to your doctor first before assuming a reaction is a sign of allergy.
• Chemicals. Some cosmetics or laundry detergents can cause people to break out in an itchy rash. Usually, this is because someone has a reaction to the chemicals in these products. Dyes, household cleaners, and pesticides used on lawns or plants can also cause allergic reactions in some people.

Some kids also have what are called cross-reactions. For example, kids who are allergic to birch pollen might have reactions when they eat an apple because that apple is made up of a protein similar to one in the pollen. Another example is that kids who are allergic to latex (as in gloves or certain types of hospital equipment) are more likely to be allergic to kiwifruit, water chestnuts, or bananas.

Signs and Symptoms

The type and severity of allergy symptoms vary from allergy to allergy and child to child. Allergies may show up as itchy eyes or an itchy nose, sneezing, nasal congestion, throat tightness, trouble breathing, and even shock (faintness or passing out).
Symptoms can range from minor or major seasonal annoyances (for example, from pollen or certain molds) to year-round problems (from allergens like dust mites or food). Allergies to dust mites are common to the eastern parts of the United States, but not in areas of high-altitude and low humidity (for example, like Colorado).
Because different allergens are more prevalent in different parts of the country and the world, allergy symptoms can also vary, depending on where you live. For example, peanut allergy is unknown in Scandinavia, where they don't eat peanuts, but is common in the United States, where peanuts are not only a popular food, but are also found in many of the things we eat.

Airborne Allergy Symptoms

Airborne allergens can cause something known as allergic rhinitis, which occurs in about 15% to 20% of Americans. It develops by 10 years of age and reaches its peak in the early twenties, with symptoms often disappearing between the ages of 40 and 60.
Symptoms can include:

• sneezing
• itchy nose and/or throat
• nasal congestion
• coughing

These symptoms are often accompanied by itchy, watery, and/or red eyes, which is called allergic conjunctivitis. (When dark circles are present around the eyes, they're called allergic "shiners.") Those who react to airborne allergens usually have allergic rhinitis and/or allergic conjunctivitis. If a person has wheezing and shortness of breath, the allergy may have progressed to become asthma.

Food Allergy Symptoms

The severity of food allergy symptoms and when they develop depends on:

• how much of the food is eaten
• the person's sensitivity to the food

Symptoms of food allergies can include:

• itchy mouth and throat when food is swallowed (some kids have only this symptom — called "oral allergy syndrome")
• hives (raised, red, itchy bumps)
• eczematous rash
• runny, itchy nose
• abdominal cramps accompanied by nausea and vomiting or diarrhea (as the body attempts to flush out the food allergen)
• difficulty breathing
• shock

Insect Venom Allergy Symptoms

Being stung by an insect that a child is allergic to may cause some of these symptoms:

• throat swelling
• hives over the entire body
• difficulty breathing
• nausea
• diarrhea
• shock

About Anaphylaxis

In rare instances, if the sensitivity to an allergen is extreme, a child may experience anaphylaxis (or anaphylactic shock) — a sudden, severe allergic reaction involving various systems in the body (such as the skin, respiratory tract, gastrointestinal tract, and cardiovascular system).
Severe symptoms or reactions to any allergen, from certain foods to insect bites, require immediate medical attention and can include:

• difficulty breathing
• swelling (particularly of the face, throat, lips, and tongue in cases of food allergies)
• rapid drop in blood pressure
• dizziness
• unconsciousness
• hives
• tightness of the throat
• hoarse voice
• lightheadedness

Anaphylaxis can happen just seconds after being exposed to a triggering substance or can be delayed for up to 2 hours if the reaction is from a food. It can involve various areas of the body.
Fortunately, though, severe or life-threatening allergies occur in only a small group of kids. In fact, the annual incidence of anaphylactic reactions is small — about 30 per 100,000 people — although those with asthma, eczema, or hay fever are at greater risk of experiencing them. Most anaphylactic reactions — up to 80% — are caused by peanuts or tree nuts.