An allergy is a condition in which the body's defense system (immune system) comes in contact with an allergen and reacts to it. An allergen is anything that causes an allergic reaction. Allergens cause the immune system to make proteins for fighting infections (antibodies). These antibodies cause cells to release chemicals called histamines that set off the symptoms of an allergic reaction.

Allergies often affect the nasal passages (allergic rhinitis), eyes (allergic conjunctivitis), skin (atopic dermatitis), and stomach. Allergies can be mild, moderate, or severe. They cannot spread from person to person. Allergies can develop at any age and may be outgrown.

What are the causes?

• Outdoor allergens, such as pollen, car fumes, and mold.
• Indoor allergens, such as dust, smoke, mold, and pet dander.
• Other allergens, such as foods, medicines, scents, insect bites or stings, and other skin irritants.

What increases the risk?

• Has family members with allergies.
• Has family members who have any condition that may be caused by allergens, such as asthma. This may make your child more likely to have other allergies.

What are the signs or symptoms?

Symptoms of this condition depend on the severity of the allergy.

Mild to moderate symptoms

• Runny nose, stuffy nose (nasal congestion), or sneezing.
• Itchy mouth, ears, or throat.
• A feeling of mucus dripping down the back of your child's throat (postnasal drip).
• Sore throat.
• Itchy, red, watery, or puffy eyes.
• Skin rash, or itchy, red, swollen areas of skin (hives).
• Stomach cramps or bloating.

Severe symptoms

• A red (flushed) face.
• Wheezing or coughing.
• Swollen lips, tongue, or mouth.
• Tight or swollen throat.
• Chest pain or tightness, or rapid heartbeat.
• Trouble breathing or shortness of breath.
• Pain in the abdomen, vomiting, or diarrhea.
• Dizziness or fainting.

How is this diagnosed?

• Skin tests to see how your child's skin reacts to allergens that may be causing the symptoms. Tests include:
  • Skin prick test. For this test, an allergen is introduced to your child's body through a small opening in the skin.
  • Intradermal skin test. For this test, a small amount of allergen is injected under the first layer of your child's skin.
  • Patch test. For this test, a small amount of allergen is placed on your child's skin. The area is covered and then checked after a few days.
• Blood tests.
• A challenge test. In this test, your child will eat or breathe in a small amount of allergen to see if he or she has an allergic reaction.

• Keep a food diary for your child. This tracks all the foods, drinks, and symptoms your child has each day.
• Try an elimination diet with your child. To do this:
  • Remove certain foods from your child's diet.
  • Add those foods back one by one to find out if any of them cause an allergic reaction.

How is this treated?

• Cold, wet cloths (cold compresses) to soothe itching and swelling.
• Eye drops or nasal sprays.
• Nasal irrigation to help clear your child's mucus or keep the nasal passages moist.
• A humidifier to add moisture to the air.
• Skin creams to treat rashes or itching.
• Oral antihistamines or other medicines to block the reaction or to treat inflammation.
• Diet changes to remove foods that cause allergies.
• Exposing your child again and again to tiny amounts of allergens to help him or her build a defense against it (tolerance). This is called immunotherapy. Examples include:
  • Allergy shots. Your child receives an injection that contains an allergen.
  • Sublingual immunotherapy. Your child takes a small dose of allergen under his or her tongue.
• Emergency injection for anaphylaxis. You give your child a shot using a syringe (auto-injector) that contains the amount of medicine your child needs. The health care provider will teach you how to give an injection.

Follow these instructions at home:

Medicines

• Give or apply over-the-counter and prescription medicines only as told by your child's health care provider.
• Have your child always carry an auto-injector pen if he or she is at risk of anaphylaxis. Give your child an injection as told by the health care provider.

Eating and drinking

• Follow instructions from your child's health care provider about eating or drinking restrictions.
• Have your child drink enough fluid to keep his or her urine pale yellow.

General instructions

• Have your child wear a medical alert bracelet or necklace to let others know that he or she has had anaphylaxis before.
• Help your child avoid known allergens whenever possible.
• Talk with your child's school staff and caregivers about your child's allergies and how to prevent them. Develop an emergency plan that includes what to do if your child has a severe allergy.
• Keep all follow-up visits as told by your child's health care provider. This is important.

Contact a health care provider if:

• Your child's symptoms do not get better with treatment.

Get help right away if:

• Your child has symptoms of anaphylaxis. These include:
  • Swollen mouth, tongue, or throat.
  • Pain or tightness in his or her chest.
  • Trouble breathing or shortness of breath.
  • Dizziness or fainting.
  • Severe abdominal pain, vomiting, or diarrhea.

These symptoms may represent a serious problem that is an emergency. Do not wait to see if the symptoms will go away. Get medical help right away. Call your local emergency services (911 in the U.S.).

Summary

• Help your child avoid known allergens when possible.
• Make sure that school staff and other caregivers know about your child's allergies.
• If your child has a history of anaphylaxis, have your child wear a medical alert bracelet or necklace and always carry an auto-injector.
• Anaphylaxis is a life-threatening emergency. Get help right away for your child.