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 basophiles (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.
How the Allergies Progress in Children?
Allergies present in different ways in different age groups. In infants and young children, allergic disease occurs as atopic dermatitis (eczema) or as food allergies. Children with atopic dermatitis are at increased risk of developing allergies and asthma, which are more likely to occur in the toddler years to school-age. This pattern of progression from one form of allergic disease to another is referred to as the “atopic march”. Atopic is a term that physicians use to mean that someone is allergic to various things (foods, environmental triggers such as pollens, molds and pet dander, for example).
Typically Atopic Dermatitis is the earliest manifestation of allergies, is seen in 10 to 20 percent of all children, and frequently seen during infancy. Atopic dermatitis, or eczema, is characterized by itching, with rash formation at the sites of scratching. The rash is typically red and dry, may have small blisters, and can flake and ooze over time.
In infants and very young children, this rash involves the face (especially the cheeks), chest and trunk, back of the scalp and may involve the arms and legs. This distribution reflects where the child is able to scratch, and therefore usually spares the diaper area. The location of the rash changes in older children to classically involve the skin in front of the elbows and behind the knees. Food and environmental allergies have been shown to worsen atopic dermatitis.
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 don’t live 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 a child is allergic to determines when symptoms will occur. 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 experience increased symptoms during those times.
Pollen counts measure how much pollen is in the air and can help people with allergies determine how bad their symptoms might be on any given day. Pollen counts are usually higher in the morning and on warm, dry, breezy days, whereas they’re lowest when it’s chilly and wet. Although not always exact, the local weather report’s pollen count can be helpful when planning outside activities.
Molds, another common allergen, are fungi that thrive both indoors and out in warm, moist environments. Outdoors, molds may 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. When the animal — often a household pet — licks itself, the saliva gets on its 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 the protein from their saliva is extremely tiny and they tend to lick themselves more than other animals as part of grooming. Pet allergens are also present in dander, hair, and urine.
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, 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 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.
Nuts are a common allergen among children and they can cause one of the more severe, even life-threatening allergic reactions known as anaphylaxis. Only about 6 percent of all children have clinically diagnosed food allergies. This number is rather small, but food intolerance, which presents itself much like a food allergy, adds to the public perception that this is a major issue. While the medical difference is quite different, the solution to a food allergy and intolerance is to remove the culprit food from you or your child’s diet.
Food allergies can be very dangerous and early detection is critical to managing them and the health of your child. Any family history of food allergies should be discussed between you and your spouse and with your healthcare provider prior to introducing solid foods to your baby. Food allergies or food intolerances can occur even if there is no previous family history of such. As you introduce your child to new foods, you should present them one at a time and watch for any changes in your child’s appearance or behavior. Some common symptoms of food allergies/intolerances include:
* Rashes or eczema, especially on the face
* Diaper rash
* Hives
* Runny nose, watery eyes or sneezing
* Diarrhea, gas or vomiting
* Irritability
* Temperament changes
* Puffy eyes
* Nasal congestion
One way to prevent food allergies is not to introduce commonly-known allergenic foods until later in your baby’s life, at one, two or even three-years-old. This approach is referred to as “delayed introduction.” The foods that children react to are those foods they eat often. The most common food allergens that cause problems in children are eggs, milk, peanuts, soy and wheat. A few more allergic foods include:
* Artificial colors and preservatives
* Berries
* Chocolate
* Citrus fruits
* Tomatoes
* Yeast
Fortunately, most allergic reactions in babies are temporary and the culprit foods can usually be reintroduced when the child is older. Food allergies can be very serious, so it is important to follow the advice that is given to you by a healthcare professional.
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.