Editors

MikaelKuitunen

Investigation of Atopy

Atopy refers to an individual disposition to produce excessive amounts of allergen-specific IgE. IgE-mediated sensitization usually occurs in childhood. Many of those sensitized, although not all, develop an atopic disease (allergic rhinitis, asthma, food allergy).
Atopy is manifested in an infant as atopic eczema and food allergy, later in childhood as allergic rhinitis and conjunctivitis as well as asthma. One person often has many of these diseases.
Treatment is aimed at patient's symptoms, not at test results. Sensitization should not be screened for.

The medical history is the most important tool for investigation of allergy.
If the patient has symptoms suggesting allergy against pollen or animals, IgE antibodies to common inhaled allergens can be measured. A positive result indicates sensitization. The patient has allergy when he/she has clinical symptoms and immunological sensitization (usually specific IgE) can be established.
Food sensitization should not be screened for. Instead, the need to investigate allergen-specific IgE antibodies is assessed based on patient history. If symptoms are mild, testing for IgE antibodies is not needed.

In clearly seasonal rhinitis Allergic Rhinitis effectively alleviated by antihistamines, nasal sprays and eye drops, allergological investigations are not mandatory. If the cause of symptoms is unclear or symptoms are difficult, investigations may help.
In persistent or intermittent rhinitis it may be useful to test for and eliminate any specific allergens (e.g. from pets).
The attitude to allergy needs changing; allergens should not be unnecessarily avoided.
Specific IgE-mediated sensitization should be verified if desensitization Allergen Immunotherapy is considered.

Basic investigations include assessment of allergies: patient history and serological IgE screening for the most common inhaled allergens.
Instructions on how to avoid allergens should be given individually depending on verified sensitization and allergy symptoms.

Atopic eczema is a disease with abnormal skin penetration, and food allergy is not its cause. If atopic eczema in an infant is not relieved by appropriate use of an emollient and intermittent use of mild glucocorticoid ointment, the possibility of food allergy should be kept in mind.
- Subsiding of the eczema during the summer speaks strongly against food allergy.
- In severe atopic eczema in an infant, affecting extensive skin areas, foodstuffs may play a part. Essential foodstuffs in the diet (milk, wheat) should be evaluated in specialized care as suggested by the child's history. Investigations should include determination of specific IgE antibodies and, as necessary, elimination-challenge testing.
A diagnosis of food hypersensitivity is based on careful history taking, elimination and challenge tests with follow-up of symptoms. Testing for IgE antibodies is done in a focused manner and extensive laboratory testing related to food should be avoided.
In older children, atopic eczema is not usually associated with food allergy (pictures 1 2), but in them pollen allergy and asthma are more common.
Investigations for food allergy: see Food Allergy and Hypersensitivity in Children children, Food Allergy in Adults adults.