Tests for allergies

Dr Th Dhabali Singh, MD *

With 1 in every 4 people suffering from it, allergy happens to be the most costly and widely prevalent health problems all over the world and more specially, in industrialised nations. Allergy is described as a malfunction of the human immune system causing a violent reaction against normally harmless substances in our natural environment. Here, such substances are generally referred to as “allergens”.

All of the risk factors for allergy are not known. However, it is generally believed that both genetic and environmental factors are of importance. People with a tendency to suffer from allergic reactions are said to be atopic.

Allergy can be antibody or cell-mediated. In the majority of cases, the antibody responsible for an allergic reaction belongs to the IgEisotype and individuals may be referred to as suffering from an IgE-mediated allergy.

SYMPTOMS OF ALLERGY:

Symptoms of allergy vary in complexity, severity and manifestation. With atopic allergies, the effect of exposure to an allergen can be immediate. Symptoms can be mild or severe, varying from itchy eyes, to eczema, rhinitis, conjunctivitis, bronchoconstriction, vomiting and diarrhoea and, in rare cases, anaphylaxis.

Chronic reactions can be seen as skin reactions (eczema) and in bronchial asthma, an ongoing lung tissue inflammation can be the reason for an asthma attack seen after exposure to the offending allergen.

Asthma attacks can also be brought about by events other than IgE-mediated reactions. Manifestations of atopic diseases vary considerably depending on the allergen involved, as well as the age of the allergic patients. During infancy, allergies to food (especially egg and milk) are the most common.

After the age of 3, most allergic children tolerate these foods, while allergy to inhalants becomes predominant. Specific IgE antibodies often precede allergy symptoms, but clinical symptoms catch up with time.

Allergy : Eczema
Symptoms : Dry skin, itchy skin, nettle rash/hives (urticaria), skin rash
Common Allergens : Food (e.g. fish, milk, eggs, wheat, soybean, peanut and hazelnut)

Allergy : Hay fever (rhinitis)
Symptoms : Blocked nose, breathing through the mouth, itchy nose, itchy throat, lips, mouth, itchy eyes, runny nose, sneezing, swelling of the mouth, weeping eyes
Common Allergens : Pollen, house-mites, cockroach, pets (cats, dogs, rabbit), and other animals like cows, horses, birds, etc.

Allergy : Eye Inflammation
Symptoms : Itchy, red eyes and swollen eyelids, weeping eyes
Common Allergens : Pollen, house-mites, cockroach, pets (cats, dogs, rabbit), and other animals like cows, horses, birds, etc.

Allergy : Gastrointestinal conditions
Symptoms : Diarrhoea, stomach pain, nausea and vomiting, weight loss
Common Allergens : Egg, milk, soybean, wheat, peanut, hazelnut, fish, fruits and vegetables

Allergy : Nettle rash/hives (urticaria)
Symptoms : Skin rash
Common Allergens : Nuts, shellfish, eggs, milk

Allergy : Asthma
Symptoms : Coughing, shortness of breath, wheezing and whistling breath
Common Allergens : Pollen, house dust mites, cockroach, pets and other animals

Allergy : Anaphylactic reactions
Symptoms : Hives, tingling and itching around the mouth, swelling around the eyes and the mouth, hypotension, nausea, vomiting, abdominal pain, asthma symptoms
Common Allergens : Peanuts, fish, soybean, milk, eggs, seeds, tree nuts, fruits, drugs, bee or wasp bites

ALLERGY DEVELOPMENT : In its early stages, allergy can appear as a seemingly benign condition, such as hay fever during pollen season. Some people gradually build up an allergic condition over several years before experiencing any symptoms. Others experience sudden, life-threatening anaphylactic shock following ingestion of a certain food or drug, or an insect bite. Additionally, some allergies that start as eczema or gastrointestinal problems can evolve into asthma, frequently involving respiratory symptoms such as hyper reactivity and obstruction of the airways.

HOW TO TEST FOR ALLERGIES? : A Total IgE test measures the level of IgE in an individual’s blood. A raised level indicates that the person is probably allergic to an allergen or a group of allergens. This test cannot identify specific allergen(s) causing the allergy. With the advancement in medical diagnosis and testing facilities, allergen-specific IgE tests are now available.

Specific IgE blood tests can be performed irrespective of a patient’s age, skin conditions, antihistamine medication and, even during pregnancy. IgE antibodies appear in human serum and plasma as a result of sensitisation to a specific allergen. Measurement of circulating IgE provides an objective measurement of the sensitisation of the allergen.

There are technologies that offer over 600 different allergens and allergen components for sensitive and specific quantitative detection of allergen-specific IgE antibodies. Although a final diagnosis should always be a based on a combination of IgE test results and a patient’s clinical history, a general rule of the thumb is that the higher the IgE antibody value, the greater the likelihood of symptoms appearing.

ALLERGY PANELS

According to the overall prevalence of the types of allergies, a laboratory usually groups the various allergies into categories called panels. Depending upon the symptoms of the allergic reaction present or suspicion of certain allergens, a person may opt for a panel that includes the most common allergies.

Some of these panels are:
o Aspergillosis (mould) Panel
o Rhinitis/Asthma Panel
o Eczema Panel
o Comprehensive Food Panel
o Vegetarian Food Panel
o Non-Vegetarian Food Panel
o Comprehensive (assorted) Panel

WHAT IS THE TREATMENT PLAN?

There is no specific cure for allergies. Treatments vary and can include antihistamines, steroids and simply avoiding allergens. They don’t cure allergies, but they may significantly reduce one’s sensitivity to the allergy triggers and reduce the allergic response.