What are allergies?

An allergy is the body’s reaction to a substance that is normally harmless. With allergies, your child’s body sees the substance as harmful or foreign, and the immune system reacts to the substances, also known as allergens. Allergic reactions are common; in fact, they affect up to 40% of children in the United States.

Read more below about allergies in children, their causes, common symptoms, and severe reactions. Understand how allergies are diagnosed through tests and exams.

What is the cause?

The immune system is the body’s natural defense against bacteria, viruses, and other foreign substances.

Before your child can have a reaction to a particular substance, the immune system must first be sensitive to it. Usually this means your child’s body must be exposed to the substance at least once. Once it is sensitive to it, your child’s body will react every time your child has contact with the substance. Most reactions are mild, but some are life-threatening.

Unfortunately, many things can cause an allergic reaction. Your child’s body may react to an allergen when breathing, swallowing, or touching it. Luckily, children often outgrow food allergies when they become adults.

The most common allergens are: 

  • Pollen, which is small particles in the air from grasses, weeds, or trees. 
  • Mold 
  • Animal dander (dried skin flakes) 
  • Dust and dust mites (very tiny bugs) 
  • Latex, which is a liquid from rubber trees that is used in many products such as gloves and toys. 
  • Medicines 
  • Insect stings and bites 
  • Foods such as shellfish, fish, eggs, milk, tree nuts, peanuts, and wheat 
  • Chemical irritants such as nickel, dyes in fabric, or cleaning products 
  • Poison oak, poison ivy, or poison sumac 

It’s worth noting that your child may have an increased risk of a reaction if other people in your family have allergies too.  

What are the symptoms of allergies? 

Allergy symptoms may go away in a few minutes without treatment, or they may last for several days.

Common allergy symptoms may include: 

  • Sneezing 
  • Itchy, watery eyes 
  • Stuffy or runny nose 
  • Swelling of the eyelids 
  • Itching, a rash, or hives (raised, red, itchy areas on the skin) 
  • Stomach pain 
  • Diarrhea 

Sometimes an allergic reaction may be severe. This is called anaphylaxis and it is a life-threatening emergencycall 911 immediately if this occurs because it can affect the whole body within minutes. Insect stings, certain foods, and drugs such as penicillin are some of the more common causes of severe allergic reactions.

Severe symptoms of a severe allergic reaction may include one or more of the following:

  • Severe trouble breathing, including wheezing
  • Swelling of the lips, tongue, or throat
  • Hives
  • Pale, cool, damp skin
  • Fast or pounding heartbeat
  • Nausea and vomiting
  • Feeling intense fear that something terrible is about to happen
  • Drowsiness, confusion, or fainting

How are allergies diagnosed? 

Your child’s healthcare provider will ask about his or her symptoms, review medical history, and examine your little one thoroughly. Most common allergies can be diagnosed from your child’s history and a physical exam.  

Tests to check for allergies may include: 

  • Blood tests 
  • A skin prick test, which uses a drop of liquid allergen extract put under your child’s skin using a needle. 
  • Elimination diet, which means your child avoids eating certain foods for a few weeks to see if allergy symptoms go away. 
  • Food challenge test, which is eating food that is a possible allergen to see if your child has a reaction. This test is done only by a healthcare provider who is ready to treat your child if your child has a serious reaction to the food. 


Book a Pediatric appointment 480-964-2273