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All About Allergies

Dust, cats, peanuts, cockroaches. An odd grouping, but one with a common thread — people can be allergic to them. Allergies are a major cause of illness in the United States. Up to 50 million Americans, including millions of kids, have some type of allergy. In fact, allergies lead to about 2 million missed school days each year.

About Allergies

An allergy happens when the immune system overreacts to something that's harmless to most people. The immune system treats the substance (called an allergen) as an invader and tries to fight it off, causing symptoms that can range from annoying to serious or life-threatening.

In an attempt to protect the body, the immune system makes antibodies called immunoglobulin E (IgE). These antibodies then cause certain cells 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. Reactions can affect the eyes, nose, throat, lungs, skin, and gastrointestinal tract. Future exposure to that same allergen will trigger this allergic response again.

Some allergies are seasonal and happen only at certain times of the year (like when pollen counts are high); others can happen anytime someone comes in contact with an allergen. So, when a person with a food allergy eats that particular food or someone who's allergic to dust mites is exposed to them, they will have an allergic reaction.

Who Gets Allergies?

The tendency to develop allergies is often hereditary, which means it can be passed down through genes from parents to their kids. But 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.

Some kids have allergies even if no family member is allergic, and those who are allergic to one substance are likely to be allergic to others.

Common Airborne Allergens

Some of the most common things people are allergic to are airborne (carried through the air):

  • Dust mites are one of the most common causes of allergies. These microscopic insects live all around us and feed on the millions of dead skin cells that fall off our bodies every day. Dust mites are the main allergic component of house dust, which is made up of many particles and can contain things such as fabric fibers and bacteria, as well as microscopic animal allergens. Dust mites are present year-round in most parts of the United States (although they're much less common at high altitudes) and live in bedding, upholstery, and carpets.
  • Pollen is another major cause of allergies (most people know pollen allergy as hay fever or rose fever). Trees, weeds, and grasses release these tiny particles into the air to fertilize other plants. Pollen allergies are seasonal, and the type of pollen someone is allergic to determines when symptoms happen. For example, in the mid-Atlantic states, tree pollination begins in February and lasts through May, grass from May through June, and ragweed from August through October; so people with these allergies are likely to have symptoms during those times.

    Pollen counts measure how much pollen is in the air and can help people with allergies predict how bad their symptoms might be on any given day. Pollen counts are usually higher in the morning and on warm, dry, breezy days, and lowest when it's chilly and wet. Although not always exact, the local weather report's pollen count can be helpful when planning outdoor activities.
  • Molds, another common allergen, are fungi that thrive both indoors and outside in warm, moist environments. Outdoors, molds can be found in poor drainage areas, such as in piles of rotting leaves or compost piles. Indoors, molds thrive in dark, poorly ventilated places such as bathrooms and damp basements, and in clothes hampers or under kitchen sinks. A musty odor suggests mold growth. Although molds tend to be seasonal, many can grow year-round, especially those indoors.
  • Pet allergens from warm-blooded animals can cause problems for kids and parents alike. Pet dander (tiny flakes of shed skin, fur, or feathers) can lead to allergies. (Contrary to popular belief, dander that causes allergies is not related to the length of an animal's fur or hair, and there is no such thing as a non-allergenic dog or cat.) Animal saliva also can be an allergen, when a pet licks someone, or licks him or herself. When pets lick themselves, the saliva gets on their fur or feathers. As the saliva dries, protein particles become airborne and work their way into fabrics in the home. Cats are the worst offenders because they tend to lick themselves more than other animals as part of grooming. Pet urine also can cause allergies in the same way when it gets on airborne fur or skin, or when a pet urinates in a spot that doesn't get cleaned.
  • Cockroaches are also a major household allergen, especially in inner cities. Exposure to cockroach-infested buildings may be a major cause of the high rates of asthma in inner-city kids.

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. Eight foods account for most of those: cow's milk, eggs, fish and shellfish, peanuts and tree nuts, soy, and wheat.

  • Cow's milk (or cow's milk protein). Between 2% and 3% of children younger than 3 years old are allergic to the proteins found in cow's milk and cow's milk-based formulas. Most formulas on the market are cow's milk-based. Cow's milk protein allergy means that someone 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 also can be a hidden ingredient in prepared foods. Many kids outgrow milk allergies.
  • Eggs. One of the most common food allergies in infants and young children, egg allergy can pose many challenges for parents. Eggs are used in many of the foods kids eat — and in many cases they're "hidden" ingredients. Kids tend to outgrow egg allergies as they get older.
  • Fish and shellfish. Fish and shellfish allergies are some of the more common adult food allergies and ones that people usually don't outgrow. Fish and shellfish are from different families of food, so having an allergy to one does not necessarily mean someone will be allergic to the other.
  • Peanuts and tree nuts. Peanut allergy is another common food allergy in kids, with the number of those who are allergic on the rise. (Peanuts are not a true nut, but a legume, in the same family as peas and lentils, although most people with peanut allergy don't have allergies to other legumes.) Another common allergy is to tree nuts, such as almonds, walnuts, pecans, hazelnuts, and cashews. Most people do not outgrow peanut or tree nut allergies.
  • Soy. Like peanuts, soybeans are legumes. Soy allergy is more common among babies than older children. Many infants who are allergic to cow's milk are also allergic to the protein in soy formulas. Soy proteins are often a hidden ingredient in prepared foods.
  • Wheat. Wheat proteins are found in many foods, and some are more obvious than others. Although wheat allergy is often confused with celiac disease, there is a difference. Celiac disease is a sensitivity to gluten (found in wheat, rye, and barley) that can make someone feel ill and damage the small intestine. But a wheat allergy can do more than make a person feel ill — like other food allergies, it also can cause a life-threatening reaction.

Other Common Allergens

  • Insect allergy. 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 sting can cause more serious symptoms.
  • Medicines. Antibiotics are the most common type of medicines that cause allergic reactions. Many other medicines, including over-the-counter medications (those you can buy without a prescription), also can cause allergic reactions.
  • Chemicals. Some cosmetics or laundry detergents can make people break out in hives. Usually, this is because someone has a reaction to the chemicals in these products, though it may not always be an allergic reaction. Dyes, household cleaners, and pesticides used on lawns or plants also can 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 symptoms when they eat an apple because that apple is made up of a protein similar to one in the pollen. And for reasons that aren't clear, people with a latex allergy (found in latex gloves and some kinds of hospital equipment) are more likely to be allergic to foods like kiwi, chestnuts, avocados, and bananas.

Signs and Symptoms

The type and severity of allergy symptoms vary from allergy to allergy and person to person. Allergies may show up as itchy eyes, sneezing, a stuffy nose, throat tightness, trouble breathing, vomiting, and even faintness or passing out. Severe allergic reactions (called anaphylaxis) can be fatal if not treated quickly.

Airborne Allergy Symptoms

Airborne allergens can cause something known as allergic rhinitis, which affects about 7% to 10% of Americans. Allergic rhinitis usually develops by 10 years of age, reaches its peak in the teens or early twenties, and often disappears between the ages of 40 and 60.

Symptoms can include:

  • sneezing
  • itchy nose and/or throat
  • stuffy nose
  • coughing

When symptoms also include itchy, watery, and/or red eyes, this is called allergic conjunctivitis. (Dark circles that sometimes show up around the eyes are called allergic "shiners.")

Food, Medicines, or Insect Allergy Symptoms

  • wheezing
  • trouble breathing
  • coughing
  • hoarseness
  • throat tightness
  • stomachache
  • vomiting
  • diarrhea
  • itchy, watery, or swollen eyes
  • hives
  • swelling
  • a drop in blood pressure, causing lightheadedness or loss of consciousness

Allergic reactions can vary. Sometimes, a person can have a mild reaction that affects only one body system, like hives on the skin. Other times, the reaction can be more serious and involve more than one part of the body. A mild reaction in the past does not mean that future reactions will be mild.

Diagnosing Allergies

Some allergies are fairly easy to identify because the pattern of symptoms after exposure to certain allergens can be hard to miss. But other allergies are less obvious because they can be similar to other conditions.

If your child has cold-like symptoms lasting longer than a week or two or develops a "cold" at the same time every year, talk with your doctor, who will ask about the symptoms and when they appear. Based on the answers and a physical exam, the doctor might diagnose an allergy and prescribe medicines, or may refer you to an allergist (a doctor who is an expert in the treatment of allergies) for allergy tests.

To find the cause of an allergy, allergists usually do skin tests for the most common environmental and food allergens. A skin test can work in one of two ways:

  1. A drop of a purified liquid form of the allergen is dropped onto the skin and the area is scratched with a small pricking device.
  2. A small amount of allergen is injected just under the skin. This test stings a little but isn't painful.

After about 15 minutes, if a lump surrounded by a reddish area (like a mosquito bite) appears at the site, the test is positive.

Blood tests may be done instead for kids with skin conditions, those who are on certain medicines, or those who are very sensitive to a particular allergen.

Even if testing shows an allergy, a child also must have symptoms to be diagnosed with an allergy. For example, a toddler who has a positive test for dust mites and sneezes a lot while playing on the floor would be considered allergic to dust mites.

Treating Allergies

There's no cure for allergies, but symptoms can be managed. The best way to cope with them is to avoid the allergens. That means that parents must educate their kids early and often, not only about the allergy itself, but also about the reactions they can have if they consume or come into contact with the allergen.

Telling all caregivers (childcare staff, teachers, family members, parents of your child's friends, etc.) about your child's allergy is also important.

If avoiding environmental allergens isn't possible or doesn't help, doctors might prescribe medicines, including antihistamines, eye drops, and nasal sprays. (Many of these also are available without a prescription.)

In some cases, doctors recommend allergy shots (immunotherapy) to help desensitize a person to an allergen. But allergy shots are only helpful for allergens such as dust, mold, pollens, animals, and insect stings. They're not used for food allergies.

Airborne Allergies

To help kids avoid airborne allergens:

  • Keep family pets out of your child's bedroom.
  • Remove carpets or rugs from your child's room (hard floors don't collect dust as much as carpets do).
  • Don't hang heavy drapes and get rid of other items that allow dust to build up.
  • Clean when your child is not in the room.
  • Use special covers to seal pillows and mattresses if your child is allergic to dust mites.
  • If your child has a pollen allergy, keep the windows closed when pollen season is at its peak, have your child take a bath or shower and change clothes after being outdoors, and don't let him or her mow the lawn.
  • Keep kids who are allergic to mold away from damp areas, such as some basements, and keep bathrooms and other mold-prone areas clean and dry.

Food Allergies

Kids with food allergies must completely avoid products made with their allergens. This can be tough as allergens are found in many unexpected foods and products.

Always read labels to see if a packaged food contains your child's allergen. Manufacturers of foods sold in the United States must state in understandable language whether foods contain any of the top eight most common allergens. This label requirement makes things a little easier. But it's important to remember that "safe" foods could become unsafe if food companies change ingredients, processes, or production locations.

Cross-contamination means that the allergen is not one of the ingredients in a product, but might have come into contact with it during production or packaging. Companies are not required to label for cross-contamination risk, though some voluntarily do so. You may see advisory statements such as "May contain…," "Processed in a facility that also processes…," or "Manufactured on equipment also used for …."

Because products without such statements also might be cross-contaminated and the company did not label for it, it is always best to contact the company to see if the product could contain your child's allergen. Look for this information on the company's website or email a company representative.

Cross-contamination also can happen at home or in restaurants when kitchen surfaces or utensils are used for different foods.

Serious Reactions (Anaphylaxis)

Kids with severe allergies (such as those to food, medicine, or insect venom) can be at risk for a sudden, potentially life-threatening allergic reaction called anaphylaxis. Anaphylaxis can happen just seconds after being exposed to an allergen or not until a few hours later (if the reaction is from a food).

Although anaphylaxis isn't common, if your child has allergies it's important to know about it and be prepared. A severe reaction can affect various areas of the body and be very frightening. It can begin with some of the same symptoms as a less serious reaction, but then quickly get worse, leading to trouble breathing, swelling in the mouth or throat, dizziness, or fainting.

With quick action, anaphylaxis can be treated. If it's not treated, it can be fatal. So doctors will want anyone diagnosed with a life-threatening allergy to carry an epinephrine auto-injector in case of an emergency. Epinephrine works quickly against serious allergy symptoms; for example, it reduces swelling and raises low blood pressure.

Available in an easy-to-carry container that is the size of a large pen, injectable epinephrine is carried by millions of parents (and older kids) everywhere they go. With an injection into the thigh, the device administers epinephrine to ease the allergic reaction.

An injectable epinephrine prescription usually includes two auto-injectors and a "trainer." The trainer has no needle or epinephrine, but lets parents and older kids practice using the device. It's very important to become familiar with and comfortable using it. Your doctor will give you instructions on using and storing injectable epinephrine.

Older kids and teens who can use injectable epinephrine by themselves should have it available at all times. At school, for instance, this means keeping it in a bookbag or purse that stays with your child, not in a school locker. If your child is younger, talk to the school nurse, teachers, and your childcare provider about keeping injectable epinephrine on hand in case of an emergency. Injectable epinephrine devices also must be available in your home and in the homes of friends and family members if your child spends time there.

It's also a good idea to carry an over-the-counter antihistamine, which can help ease allergy symptoms in some people. But antihistamines should not be used as a replacement for the epinephrine pen. Doctors also might encourage kids to wear a medical alert bracelet. 

Kids who have had to use injectable epinephrine should go immediately to a medical facility or hospital emergency department, where further treatment can be given if needed. Up to 1 in 5 anaphylactic reactions can cause a second wave of symptoms several hours after the first attack. Anyone who has had a serious reaction should be watched in a clinic or hospital for several hours, even if they seem fine.

The good news is that serious or life-threatening allergic reactions are rare. In fact, each year anaphylactic reactions account for only a tiny percentage of overall allergic reactions. With proper diagnosis, prevention, and treatment, most kids can keep their allergies in check and live happy, healthy lives.