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Blomia tropicalis extract is an allergen extract prepared from the Blomia tropicalis house dust mite. It is classified as an allergen extract under the ATC code V01AA. This substance is an investigational diagnostic product: it has no marketing authorisation in the product records, meaning it is not yet approved as a medicine. The product is supplied by INMUNOTEK S.L. and appears in trial records under the product name "Prick test of blomia tropicalis extract".[1]
Blomia tropicalis is a mite species found in house dust, particularly in tropical and subtropical regions. It is a common source of indoor allergens that can trigger allergic reactions in sensitised people. The extract is being developed specifically for use in skin prick testing, a diagnostic procedure that helps identify whether a person is allergic to this mite.[3]
In a skin prick test, a small drop of the allergen extract is placed on the skin, and the skin is pricked through the drop. If a person is sensitised to Blomia tropicalis, the immune system reacts locally: immune cells in the skin release histamine and other substances, producing a raised, red, itchy bump called a wheal. The size of this wheal indicates how strongly the person reacts to the allergen. The extract is being studied to find the concentration that produces a wheal similar in size to the one caused by a standard histamine solution, which serves as a positive control.[1]
The extract is formulated as a solution for skin-prick test and is given by cutaneous use, meaning it is applied to the surface of the skin. In the trials, a small number of drops (2 drops per application) are used. The Phase 3 trial specifies a concentration of 450 µg/mL for one of the tested preparations.[2]
Two clinical trials of blomia tropicalis extract are registered in the EU Clinical Trials Information System. Both are interventional studies in people with allergy to Blomia tropicalis. The first is a completed Phase 2 trial with 30 participants, which aimed to determine the concentration of the extract that induces a wheal of the same size as a 10 mg/mL histamine dihydrochloride solution.[1] The second is an authorised Phase 3 trial planning to enrol 70 participants, designed to measure the sensitivity and specificity of different concentrations of the extract for the skin prick test.[2]
The main measurement in both trials is the area of the wheal induced on the skin, expressed in square millimetres (mm²). The trials compare the wheal produced by the blomia tropicalis extract with the wheals produced by positive and negative controls. The positive control is a histamine solution, and the negative control is a solution without the active allergen. The Phase 3 trial also aims to calculate additional parameters such as efficiency, positive and negative predictive values, and probability ratios, which will help choose the optimal concentration for diagnostic use.[2]
The supplementary sources provided do not report specific side effects for blomia tropicalis extract. Skin prick testing generally involves a small local reaction at the test site, but no side effect data for this extract were available in the provided materials.
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