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What is Allergy Diagnosis?

  • Posted By: Dr Puneeth KN
  • Allergy Diagnosis
  • Comments: 3

Introduction

Allergy Diagnosis is based on a combination of the person’s clinical history, family history, physical examination, skin tests and laboratory tests. These tests serve to confirm the diagnosis of allergic disease and to identify potential allergic triggers, knowledge that is useful to guide allergen avoidance strategies.

Your doctor uses the following information to make a diagnosis of allergy:

  • History:The diagnosis of allergy begins with a clinical history. Your doctor will ask questions about your general health and then will focus on allergies and conditions that commonly coexist with allergic disorders, such as asthma and eczema (atopic dermatitis). Your doctor will need to know all the symptoms that are troubling you.
  • Family History:Your doctor will ask you whether any of your close relatives have allergic symptoms and whether they have been diagnosed with an allergic disorder such as asthma, hay fever or eczema, or allergic sensitivity to foods or medications.
  • Physical Examination:Your doctor will perform a complete physical exam with special emphasis on your eyes, ears, nose, throat, chest and skin.
  • Allergy Tests:Allergy testswill likely be performed to determine whether you are allergic and what you are allergic to. Skin tests are carried out by applying drops of allergens to your skin and then scratching or pricking though them. Blood tests may also be performed to evaluate for the presence of sensitizing antibodies.

Is it allergy?

Allergy can be defined as a detrimental immune-mediated hypersensitivity response to common environmental substances. While the word “allergy” can mean many things literally, but clinically the diagnosis of allergies is critically dependent on identifying the immune processes involved in the allergic response.

The immune processes of allergy usually rely on the production of IgE antibodies specific to common allergens. Allergic diseases are caused by the activation of mast cells and basophils through cell-surface-bound IgE. This causes the release of histamine and other mediators, leading to allergic inflammation.

Chronic allergic inflammation characteristically involves a cellular tissue infiltrate of eosinophils and lymphocytes associated with chronic tissue damage. This is mediated by T cells rather than IgE.

A useful test for the clinical diagnosis is to ask whether the symptoms are IgE-mediated (IgE-mediated symptoms include asthma, rhinitis, urticaria, eczema, food hypersensitivity and anaphylaxis). If not, then the symptoms are unlikely to be the result of true allergy.

IgE is produced by B lymphocytes directed by cytokine release from T helper lymphocytes. In people with allergies, the T helper lymphocytes secrete cytokines that stimulate the production of IgE antibodies to allergens. The condition of secreting IgE in response to common environmental allergens is called “atopy”.

Predisposition to atopy is determined by both genetic and environmental influences, particularly in infancy, when immune responses to allergens are maturing, and T lymphocyte cytokine production is influenced by environmental exposures.

The Allergy Diagnosis depends on identifying both the symptoms on allergen exposure and the relevant allergen specific IgE. The manifestation of allergic diseases changes throughout life: food allergies and eczema are most likely to develop in infants, asthma in young children, and rhinitis in older children and adults. There is increasing evidence that appropriate treatment of allergies can prevent and alter the natural history of allergic diseases. Optimal treatment requires accurate determination of allergic triggers. Moreover, if an allergen avoidance strategy is to be pursued in relation to food or aeroallergens, it is critical to minimize the inconvenience of this strategy by making a correct diagnosis as early as possible.

Detecting allergen-specific IgE

Accurate diagnosis of allergic disease and the relevant allergens helps to determine appropriate treatment options. Allergen-specific IgE can be detected by skin prick testing and by blood specific IgE testing (ie, serum allergen-specific IgE testing [as distinct from total IgE testing]).

Skin prick testing

Skin prick testing relies on the introduction of a very small amount of allergen extract into the epidermis using a standardized method to ensure reproducibility and comparability of results. The results of skin prick testing are read at 20 minutes. The diameter of the resulting wheal is recorded in two dimensions and the average of it is recorded.

Where standardized reagents are not available, crude allergens can be used for testing, but the results require interpretation by an Allergy Specialist.

Intradermal allergy testing (in which a small amount of diluted allergen is injected into the dermis) has a very high non-specific reaction rate, but is useful in specific protocols for investigating drug and stinging insect allergy.

Other methods of skin testing such as “scratch”testing are no longer used, owing to inconsistency of results.

Blood specific IgE testing

Blood specific IgE testing to a wide range of allergens detects and quantifies allergen-specific IgE. It can be used to diagnose all types of allergies, but is generally less sensitive than skin prick testing. Blood specific IgE testing is particularly useful when anaphylaxis is being investigated, as testing carries no associated risk of anaphylaxis and there are very few contraindications.

Blood specific IgE testing can be performed in patients who are taking antihistamines or other drugs that are contraindicated in skin prick testing, and in patients whose risk of an adverse reaction to skin prick testing is high (eg, those with unstable asthma or anaphylaxis).

Blood specific IgE testing can be difficult to interpret in patients who have very high levels of total IgE (>1000kU/L) (eg, patients with eczema), as they may have low-grade reactions to many allergens. Although blood specific levels of Ig G antibodies, especially to food allergens, can be measured, such testing should not be requested, as there is no evidence that it is relevant to allergy diagnosis.

Reasons to see an Allergy Specialist:

Many people with allergies see a primary care doctor for allergy care. You may choose to visit an Allergy Specialist, which is a doctor who specializes in allergies, for your allergy testing and treatment.

Here are a few reasons for seeing an allergy specialist:

  • Your regular doctor refers you to an expert for specialized tests.
  • Your symptoms interfere with your daily activities.
  • Your symptoms are getting worse.
  • You are concerned about side effects of medicine.
  • You are interested in different types of therapies to treat your symptom

If you have any allergy related issues feel free to contact Allergy Specialist in Bangalore - Dr. Puneeth KN for a consultation.

About the Author

Dr. Puneeth KN

Dr Puneet. K. Nagendra

MBBS, DTCD, DNB (Pulmonary Medicine)

Presently I render my clinical services as an Allergist & Pulmonologist in Bengaluru Allergy Centr, PD Hinduja Sindhi Hospital, Excelcare Hospital and Mahapranajeeva - Speciality Centre for Respiratory diseases at Bengaluru.

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