What Are Allergies?

Allergies are abnormal immune system reactions to things — known as allergens —that are typically harmless to most people. This causes symptoms that can range from just annoying to possibly life-threatening. Common allergens include some foods, dust, plant pollen, and medicines.

Many adults and kids have some type of allergy.

How Do Allergies Happen?

If a child with an allergy is exposed to that allergen, their immune system mistakenly believes it's harming their body. It overreacts, treating the substance as an invader and trying to fight it off. To protect the body, the immune system makes antibodies called immunoglobulin E (IgE). These 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.

What Are the Kinds of Allergies?

Common types of allergies include:

Airborne Allergies

These include:

• dust mites
• pollen (often called hay fever)
• molds
• pets
• cockroaches

Food Allergies

These are the top causes of food allergies in kids:

• cow's milk(or cow's milk protein)
• eggs
• fish
• shellfish
• peanuts and tree nuts
• soy
• wheat
• sesame

Other Common Allergies

• insect sting allergy
• medicines, such as antibiotics and some over-the-counter medicines
• 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. Dyes, household cleaners, and pesticides also can cause allergic reactions in some people.

Why Do Kids Get 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 a parent has allergies doesn't mean that their kids definitely will get them. 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. Kids who are allergic to one thing often are allergic to others.

Some kids also have cross-reactions. For example, kids who are allergic to birch pollen might have symptoms when they eat an apple because that apple contains 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.

How Are Allergies Diagnosed?

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 might diagnose an allergy and prescribe medicines, or may refer you to an allergist (a doctor who diagnoses and treats allergies) for allergy tests.

To find the cause of an allergy, allergists usually do skin tests for the most common environmental and food allergens. They might do blood tests instead for kids with skin conditions, who are on certain medicines, or 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. So, 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.

How Are Allergies Treated?

There's no cure for allergies, but symptoms can be managed. The best way to cope with them is to avoid the allergens. Parents should talk to their kids often about the allergy itself and the reactions they can have if they consume or come into contact with the allergen.

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

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

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