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What are allergies?

Allergies are overreactions of the immune system. They happen when the immune system fights harmless foreign substances called allergens, such as dust mites, pollen, pet dander, and food. Therefore, treatments are usually designed to suppress the allergic reaction so your child can be safely exposed to the allergens and/or treat the symptoms when they occur.

Visible allergy symptoms are the body’s reaction to inflammatory chemicals, such as histamines, cytokines, or leukotrienes. Inflammatory chemicals are released from white blood cells to fight foreign substances in the body. Each time your child sneezes or shows some symptom of an allergic reaction, her body is reacting to the allergen. Specifically, the immune system makes immunoglobin E (IgE) antibodies to the allergens, which causes mast cells to release chemicals such as histamines, cytokines, and leukotrienes to fight the allergens. Essentially, the reaction between the IgE and the allergen triggers an allergic reaction.

The process is similar for food allergies. One difference is that with a food allergy, a child is more likely to have dermatologic (skin symptoms) and gastrointestinal symptoms, such as cramps, nausea, and vomiting, than with an inhalant allergy.

Allergies in Children | Symptoms & Causes

What are some symptoms of an allergic reaction?

  • Rhinitis: nasal stuffiness, sneezing, nasal itching, nasal discharge, itching in ears or roof of the mouth
  • Allergic conjunctivitis: red, itchy, watery eyes
  • Atopic dermatitis: red, itchy, dry skin
  • Urticaria: hives or itchy welts
  • Asthma: shortness of breath, coughing, wheezing
  • Food allergies can be life-threatening. It is important to know the symptoms of a food allergic reaction. See our section on food allergies for signs and symptoms.

What causes an allergic reaction?

Allergens can be breathed in through the air and enter the nose, sinuses, throat, or lungs. Additionally, allergens can enter through the skin with direct physical contact or can be ingested in the case of food allergies.

Some of the allergens that may trigger an allergic reaction are:

Patterns of allergies have been found in families; however, the specific genetic factors are not yet fully understood.

Allergies in Children | Diagnosis & Treatments

How are allergies diagnosed?

The first step in treating your child is forming an accurate and complete diagnosis. If you suspect that your child is allergic to something specific, skin testing can confirm it. During this test, liquid-form extracts of the allergens are placed on the top layer of the skin through a pricking device. If the suspected allergen is indeed causing the allergic reaction, the skin will turn red where the test was applied. Skin testing usually yields results faster than blood tests.

In some situations doctors might do intradermal testing, meaning the allergen being tested for would be injected under the top layer of the skin. For example, a child might have venom testing to see if she’s allergic to stinging insects: She’d have a histamine place on her skin, and then a small amount of venom injected under the top layer of the skin. If at either step the skin develops a red spot, it means your child has an allergy to the venom, such as from a bee or wasp.

A measurement of specific IgE can help indicate if your child has allergies based on the level of IgE antibodies in their bloodstream. In reaction to allergens, the body typically produces more IgE antibodies; thus, higher IgE antibodies levels would indicate your child has allergies.

After any of these tests, your child’s doctor will review and discuss the results to outline the best treatment plan for your child.

How are allergies treated?

Limiting exposure to allergens

  • Remain indoors when the pollen count is high and on windy days. Pollen is especially high from 5 to 10 a.m.
  • Dust-proof your home, particularly your child's bedroom.
  • Reduce wall-to-wall carpet, Venetian blinds and down-filled blankets or pillows.
  • Wash bedding, curtains and clothing often in hot water to eliminate dust mites.
  • Keep bedding in allergen proof mattress and pillow encasings.
  • Use air conditioning instead of opening the windows.
  • Use a dehumidifier in damp areas of the home and remember to clean it often.
  • Don't leave wet clothes in the washer. Damp clothes can be a safe haven for mold.
  • Avoid secondhand cigarette smoke
  • Talk with your child's school to determine high risk areas and activities.
  • If your child plays sports, inform the coaches about your child's allergies.

Immunotherapy (allergy shots)

  • Used for children with hay fever and/or asthma.
  • Also called desensitization, hyposensitization and allergy shots.
  • The shots are a mixture of the various pollens, molds, animal dander and dust mites to which your child is allergic. They contain no medication such as antihistamines or corticosteroids.
  • Injected into the fatty tissue in the back of the arm. It isn't painful like an injection into the muscle, such as a penicillin shot.
  • Given weekly or twice a week until a maximum dose is tolerated. This is called the maintenance dose. It may take about one year to reach the maintenance dose. At this point, the frequency of injections may be decreased to every other week and finally to once a month.
  • About 80 to 90 percent of children improve with immunotherapy. It usually takes 12 to 18 months before definite reduction in allergy symptoms is noticed, but can take as few as six months. It's important to continue allergy medications and avoidance in the meantime.

There are some side-effects to immunotherapy

  • Local: redness and swelling at the injection site. If this happens, your doctor will change the extract strength or schedule.
  • Systemic: involves a site other than the injection site. Symptoms may include nasal congestion, sneezing, hives, swelling, wheezing and low blood pressure. Such reactions can be serious and life threatening (deaths related to immunotherapy are rare). If a serious reaction occurs, your doctor will lower the dosage.


The American Academy of Pediatrics recommends against some over-the-counter medicines for infants and young children. Always consult your child's physician before giving your child any over-the-counter medications.


  • Used to relieve or prevent the symptoms of allergic rhinitis (hay fever) and other allergies
  • Prevent the effects of histamine, a substance produced by the body during an allergic reaction
  • Come in tablet, capsule, liquid, or injection form and are available both over-the-counter and by prescription


  • Cause the blood vessels to narrow, leading to the clearing of nasal congestion
  • Come in tablet, liquid and nose spray, or drops, and are available both over the counter and by prescription
  • The American Academy of Family Physicians does not recommend decongestants for children ages 4 and younger

How we care for allergies

Boston Children’s Hospital's Allergy and Asthma Program physicians collaborate with your child’s primary care physician to provide a comprehensive and individualized treatment plan. To help treat individuals with severe atopic dermatitis, we have a multi-disciplinary Atopic Dermatitis Center with a psychologist and a nutritionist. Additionally, our team collaborates with Children’s researchers to conduct clinical trials to evaluate new approaches to allergy treatments.

What makes the Division of Immunology at Boston Children’s unique is the involvement of our researchers. Our scientists see patients, as well as conduct lab research, which helps to raise the level of patient care and brings innovative discoveries directly to our young patients.

Allergies in Children | Programs & Services