Infant Allergy Testing - An Overview

Introduction:

The Asthma and Allergy Foundation of America (AAFA) estimates that about 40 percent of children in the United States are affected by allergies. This is considered the most common chronic disease (long-standing disease). Various triggering factors can initiate allergies in children and occur at any age. Parents can consult a pediatrician (child specialist) or an allergist (doctors who are experts in treating allergies) to resolve the issue.

What Causes Allergies in Infants?

The common allergy-causing agents are:

Food Allergies: These include the following:

• Eggs.

• Peanuts.

• Milk.

• Fish.

• Soy.

• Shellfish.

• Nuts from trees.

• Wheat.

Other Allergy-Causing Agents: These include the following:

• Medicine.

• Insects.

• Pollen grains (most common).

• Mold.

• Pets.

• Mites.

What Is the Body’s Response to Allergies?

The body’s immune system fights against bacteria, viruses, and other infections by producing antibodies. However, in infants, this response can be exaggerated with exposure to certain agents, and the immune system sends more chemicals to fight against these agents, thereby causing allergies. The main substance, immunoglobulin E (IgE), is responsible for fighting against allergies. Therefore, in vitro (tests conducted outside the body) allergen-specific IgE (sIgE) testing or skin test can be performed to identify allergies in suspected cases.

Do Allergies Progress With Age?

Certain infants develop allergies during particular climatic conditions and need few exposures to become used to them. Allergic response to external agents usually occurs after three years. However, it can extend up to 6 years, whereas the allergic response to internal agents can develop in less than one year as exposure to these agents is frequent. The pattern in which allergies evolve in kids is called the ‘ allergic march’ (as it moves forward). The allergic march includes:

• Eczema - This is a common type of itchy skin rash and is seen in kids with allergies at some point.

• Food Allergies - These allergies develop around one year in response to certain food types and can persist lifelong.

• Asthma - Asthma can develop between one to two years of age and is characterized by wheezing and coughing.

• Allergic Rhinitis - It is also called 'hay fever' and can occur in response to pollen, mold, dust mites, or from trees and plants.

These allergic diseases progress from infancy to childhood and can occur in different orders.

What Are the Signs and Symptoms of Allergies?

The following are the general signs and symptoms of allergies:

• Skin rashes.

• Difficulty in breathing.

• Coughing.

• Runny nose, frequent sneezing, and congestion (more common at night).

• Upset stomach.

• Itchy eyes.

• Asthma.

Cold-like symptoms can persist for a long time or happen around the same time yearly.

The signs and symptoms of food allergy are:

• Swelling of the lips, tongue, or throat.

• Infantile colic (crying in infants for longer duration).

• Nausea and vomiting.

• Diarrhea.

• Abdominal pain.

• Loose or frequent stools.

• Blood or mucus in stools.

• Constipation.

• Food refusal.

• Paleness and tiredness.

• Gastroesophageal reflux disease (GERD).

When Should an Allergy Test Be Taken?

An allergy test can be taken when the above signs and symptoms are noticed or if there is a disturbance in the infant’s diet, sleep, and overall health. It is important to consult a physician immediately if there is an allergic response to a specific food or if cold-like symptoms last longer than a week.

What Will a Healthcare Provider Do in Cases of Allergies in Infants?

A pediatrician or an allergist (experts in treating allergies) will initially look out for physical symptoms, and ask for a history related to the onset of the disease (like the duration between food intake and the appearance of symptoms in case of food allergies), how often the symptoms occur and familial history of allergies. This history-taking is important and is the primary step to identify the cause of allergy, as allergy tests alone are not conclusive in arriving at a diagnosis.

What Are the Various Infant Allergy Testing Methods?

Skin tests are usually not performed in infants under six months as they may be less accurate. The common allergy testing methods include:

• Skin Prick Test - Antihistamines (drugs used to treat allergies) must be stopped before the test. A few drops of allergy-causing agent (allergen) are put on the skin (on the forearm or back), and a prick is made so the allergen flows inside the skin. In case of a positive response, a small reddish bump surrounded by a ring is noticed within 15 to 20 minutes. The procedure is usually painless. However, there can be mild itchiness, which is resolved by using a skin cream or antihistamine.

• Patch Test - This is similar to the skin prick test, but the allergens are placed on the skin as patches rather than pricking or injecting. Several suspected patches of allergens are put on the arm or back for 48 hours. The physician later removes these.

• Intradermal Test (Skin Injection Test) - It detects allergies due to vaccines, insect venom, Penicillin, or inhaled allergens. The intradermal test involves injecting the allergen into the deep layers of the skin and can be highly sensitive. A positive result shows a skin reaction at the injection site after 15 minutes. The test is usually done at the doctor’s office.

• Blood Test - A blood sample is taken and sent to the laboratory for testing. The blood is assessed for the level of antibodies (IgE antibodies) in response to different allergens.

• Food Challenge Test - The test involves introducing the child to a single suspected food-causing allergy at different intervals and observing closely for any adverse reactions. This is a lengthy procedure, usually done at the doctor’s office, so medical intervention can be gained immediately in case of serious reactions. The child should not eat after midnight before the day of the test and must have only clear liquids. The Food Allergy and Research organization (FARE) considers it the gold standard procedure for diagnosing food allergies.

• Elimination Diet - This involves the elimination of specific foods such as milk, soy, or any other suspected food identified to cause allergy in the child. The suspected food is completely stopped for two to three weeks, the child is observed for any allergic response, and if the allergist instructs to proceed with the food, the food is given in small quantities and noted for allergic response. This involves checking only one food at a time.

What Are the Advantages and Disadvantages of Skin Tests and Serologic (Blood) Tests?

1. Skin or Patch Test:

Advantages:

• Immediate results.

• Cost-effective.

• Less painful.

Disadvantages:

• Lack of quality, technique, and interpretation.

• Need to stop antihistamine drugs before the test.

• Rash-free skin.

• Difficult to perform in infants due to lack of cooperation.

• Requires hospital setup to manage adverse reactions, if any.

2. Blood Test:

Advantages:

• Need not stop antihistamine drugs prior to the test.

• Easily available.

Disadvantages:

• Expensive.

• Painful.

• Delayed results.

Despite certain limitations, each procedure is sensitive to specific allergens and helps to identify the cause.

How to Overcome Allergies in Infants?

There are different methods to manage allergies. These include:

• Food Allergies - The healthcare provider will educate on how to avoid certain foods and prescribe emergency drugs like Epinephrine for severe allergies.

• Allergens at Home - In case of allergens like dust, and mites, the house should be kept clean, and pillow covers and other bedding should be washed and changed frequently. If pets are a source of allergy, they must not be allowed to enter the bedroom, and infants must be kept away from them. The humidity level at home must be maintained at or below 50 percent.

• For Environmental Allergies - Antihistamines or nasal decongestants (medicines that relieve nose congestion) can be used as per the doctor’s guidance in case of allergies concerning specific climatic conditions. Allergy shots (injections containing small doses of allergens) can be given to kids between three to five years old.

• Breast Milk - Feeding breast milk to infants under six months can help avoid food allergies.

Conclusion:

Various allergies can occur due to various reasons. It is advisable to consult a child specialist (pediatrician) in case of any noticeable allergic signs or symptoms. Allergy tests do not always give confirmatory results and can yield false positive results. Parents are advised to record the signs and symptoms of allergy in infants along with the frequency and duration so that it will be helpful for pediatricians to assess the condition. Evaluation through proper history plays an important role in guiding further investigation, and allergy tests should be partially relied upon as the primary source of diagnosis.