Allergological History Taking
Before ordering any laboratory or instrumental tests, the clinician must evaluate the overall clinical picture. A detailed patient interview helps narrow down the list of suspected allergens and select the optimal diagnostic approach.
Particular attention is paid to previous adverse reactions to therapeutic sera and medications. Additionally, the following factors are thoroughly analyzed:
- Environmental exposures: Identifying household or occupational hazards that the patient regularly contacts.
- Genetic factor: Assessing a family history of allergic reactions in blood relatives.
- Chronobiology: Establishing the seasonality of symptom onset (e.g., exacerbations during specific plant pollination periods).
Skin Prick Tests
Skin prick tests are a foundational diagnostic method for identifying sensitization. Standardized panels of allergens are used: food, pollen, indoor allergens (dust mites), insect venom, and others.
Procedure Technique:
- The test is typically performed on the skin of the volar forearm or back.
- Drops of suspected allergens are placed on the skin surface (up to 10–20 antigens per session).
- A superficial scratch (prick) of the epidermis is made through each drop using a specialized lancet.
Evaluation of Local Reaction (Interpretation):
- Negative result: Skin changes are completely absent.
- Doubtful result: Only slight hyperemia (redness) is observed around the scratch.
- Positive result: A characteristic wheal forms at the site. The severity of the allergic reaction is directly proportional to the size of this wheal.
Provocation and Patch Tests
If skin prick tests are uninformative or further diagnosis is required, other modalities are applied, depending on the type of pathology and the route of antigen exposure.
Provocation Tests Their main goal is to model an allergic reaction through direct contact of the allergen with the target organ, referred to in allergology as the "shock organ." Routes of administration vary:
- Intranasal — applying the allergen to the nasal mucosa.
- Oral — administration via the gastrointestinal tract.
Patch Tests (Epicutaneous Tests) This method is the primary diagnostic indication for contact dermatitis. Special adhesive chambers containing the allergens are applied to the patient's skin for an extended period (up to 48 hours). After removal, the clinician evaluates the result: the test is considered positive if inflammatory lesions (erythema or papules) are identified.
Laboratory Diagnostics: Cytokines and IgE
Immunological blood tests confirm the allergic etiology of a disease. The primary laboratory markers are:
- Cytokine profile: Evaluating activity skewed toward the $T_{H}2$-type. Interleukins IL-3, IL-4, and IL-13 are of particular importance because they drive the excessive synthesis of immunoglobulin E.
- Immunoglobulin E (IgE) level: Under physiological conditions, this protein is virtually undetectable in serum. In allergic pathology, its concentration increases exponentially.
Importance of Differential Diagnosis Clinicians must consider the possibility of false-positive results. A spontaneous elevation in IgE may indicate pathologies other than allergies, including:
- Parasitic infestations (helminthiases).
- Fungal infections (mycoses).
- Viral infections (including HIV).
- Oncohematological disorders (e.g., lymphomas).