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Sensitivity and Specificity of Blomia tropicalis Extract, Histamine Dihydrochloride and Sodium Chloride in Skin Prick Test for Patients with Blomia tropicalis Allergy

InvestigationalNo placebo
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What is this trial about?

A plain-language summary of the goals, design and what participants do

The study focuses on Allergy to Blomia tropicalis, a condition in which the immune system reacts to proteins from the dust‑mite species Blomia tropicalis extract. The reaction is checked using a skin prick test, a simple procedure where a tiny amount of the extract is placed on the skin and the surface is lightly pricked to see if a small raised bump (wheal) forms.

The purpose of the study is to find out how well different strengths of the extract identify true allergic reactions (sensitivity) and avoid false positives (specificity). Participants will receive the test extract, a positive control containing histamine dihydrochloride that always causes a reaction, and a negative control with sodium chloride that should not cause a reaction. The size of any wheal that appears will be measured, and any side effects will be recorded.

Each participant will attend a short visit during which the three solutions are applied to the skin, the reactions are observed, and safety checks are performed. After the visit, participants are monitored for any delayed reactions, and the data are used to decide the best concentration of the allergen extract for future diagnostic use.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial Study Visit

    You arrive at the clinic on the day you are scheduled to begin the study.

    The study staff confirms your identity and explains the procedures that will be performed today.

  2. Step 2

    Skin Prick Test Procedure

    A small amount of three solutions is placed on the skin of your forearm:

    Blomia tropicalis extract (2 drops) to test your reaction to the allergen.

    Histamine dihydrochloride (2 drops) as a positive control that should cause a mild reaction; histamine is a substance that normally produces a small skin response.

    Sodium chloride (2 drops) as a negative control that should not cause a reaction; sodium chloride is simply salt solution used to show what a non‑reactive result looks like.

    Each drop is gently pricked through the skin with a sterile lancet.

    The entire prick test takes about ten minutes to complete.

  3. Step 3

    Measurement of Reactions

    After the pricks, the size of the raised skin areas (wheals) is measured in square millimeters.

    These measurements are recorded to assess how strongly you react to the allergen compared with the controls.

  4. Step 4

    Observation for Safety

    You remain in the clinic for at least thirty minutes while staff watch for any immediate side effects such as itching, swelling, or systemic reactions.

    If a reaction occurs, appropriate medication may be given, but the specific medication and dose are determined by the medical team at that time.

  5. Step 5

    Study Completion

    After the observation period, no further study visits or medication are required.

    The data collected from the skin test are used to evaluate the test’s accuracy.

Who can join the trial?

12 criteria

  • Signed and dated informed consent form agreeing to take part in the study.
  • Age between 12 and 70 years, any gender.
  • Positive clinical history of inhalant allergy (such as runny nose, sneezing, itchy eyes, or asthma) to other perennial allergens or pollens, but not to Blomia tropicalis (for participants who will be “true negatives”).
  • Positive clinical history of inhalant allergy (such as runny nose, sneezing, itchy eyes, or asthma) to Blomia tropicalis (for participants who will be “true positives”).
  • Negative prick test to a standardized extract of Blomia tropicalis – the raised bump (wheal) must be smaller than 7 mm² (for true negatives).
  • Positive prick test to a standardized extract of Blomia tropicalis – the raised bump (wheal) must be at least 7 mm² (for true positives).
  • Specific IgE blood level (a type of antibody) to Blomia tropicalis less than 0.35 kU/L (for true negatives).
  • Specific IgE blood level to Blomia tropicalis greater than 0.35 kU/L (for true positives).
  • Positive reaction to the positive control (histamine solution) – the wheal must be at least 7 mm² (average diameter ≥ 3 mm).
  • Negative reaction to the negative control – the wheal must be smaller than 7 mm².
  • Women of child‑bearing age must have a negative urine pregnancy test and confirm their last menstrual period at enrollment.
  • Women of child‑bearing age must agree to use a highly effective contraception method during the trial and for 72 hours after the last dose. Acceptable methods include combined hormonal pills, pro‑gestogen‑only pills, injectable or implantable hormones, intrauterine device (IUD) or hormone‑releasing system, permanent tubal blockage, a partner who has had a vasectomy, or complete sexual abstinence.

Who cannot join the trial?

12 criteria

  • You have active hives (red, itchy skin bumps), severe skin that reacts when scratched (dermographism), severe eczema (atopic dermatitis), sunburn, eczema, or psoriasis on the area where the test will be done, because these can cause false‑positive results.
  • You are allergic to phenol, a chemical sometimes used in medical products.
  • You are currently pregnant or are breastfeeding.
  • You have received allergy shots (immunotherapy) in the past five years or are currently using a B. tropicalis allergy extract.
  • You have strong symptoms of runny nose and itchy eyes (rhinoconjunctivitis) or lung asthma (bronchial asthma) and cannot stop taking allergy medicines (antihistamines) before the test.
  • You have ever had a severe bad reaction during a skin prick allergy test before.
  • herpes simplex (cold sores) or herpes zoster (shingles) on the skin where the test will be performed.
  • You are medically unstable at the time of the study, such as having an asthma attack, a fever, or other acute illness.
  • You have a serious mental health condition that could affect participation.
  • You are taking beta‑blocker medications, which are used for heart or blood‑pressure problems.
  • You are using medicines that can change the skin’s reaction, such as antihistamines.
  • You have any condition that makes the use of epinephrine (adrenaline) unsafe, such as an overactive thyroid (hyperthyroidism), high blood pressure (hypertension), or heart disease.
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Investigated drugs

  • Blomia tropicalis extract

    is a liquid preparation made from the dust‑mite allergen *Blomia tropicalis*. In this study it is placed on the skin and a tiny needle prick is made. If a person is allergic to this dust‑mite, the area will become red and swollen, showing a positive reaction. The test helps researchers see how well the extract can identify people who are truly allergic (sensitivity) and how well it avoids false positives (specificity).

  • Histamine (positive control)

    is a solution used during the skin prick test to make sure the test works correctly. Histamine always causes a small skin reaction, such as a bump or redness, in anyone who receives it. By comparing this known reaction to the reaction from the allergen extract, doctors can confirm that the test was performed properly.

  • Sodium chloride (negative control)

    is a simple salt water solution applied to the skin during the prick test. It should not cause any skin reaction. This helps show that any redness or swelling seen with the allergen extract is due to an allergic response and not because of the test procedure itself.

What is already known about the treatment

  • Blomia tropicalis extract

    This allergen extract is supplied as a liquid solution for skin‑prick testing and is applied by placing a small drop on the skin followed by a gentle puncture. It is currently used only as a diagnostic tool and is listed in medical literature under allergen extracts (ATC V01AA). The main purpose is to identify people who are allergic to the dust‑mite species Blomia tropicalis. It works by presenting natural proteins that bind to IgE antibodies in sensitized individuals, causing a localized skin reaction, and it belongs to the pharmacological class of allergen extracts.

  • Histamine dihydrochloride

    This compound is provided as a liquid solution for skin‑prick testing and is applied in the same way as a drop on the skin with a small prick. It is widely used as a positive control in allergy tests and is recognized in the medical literature as a standard test substance (ATC L03AX14). Its role is to produce a predictable skin wheal, confirming that the testing method is working correctly. Histamine directly stimulates skin histamine receptors, causing a short‑lasting redness and swelling, and it is classified as a histamine agent.

  • Sodium chloride

    This isotonic saline solution is used for skin‑prick testing and is applied as a drop on the skin followed by a gentle prick. It serves as the negative control in allergy testing and is listed in medical references under test substances for allergic diseases (ATC V04CL). Its purpose is to show the baseline response when no allergen is present. Because it is simply salt water, it does not trigger an immune reaction, and it belongs to the pharmacological class of saline solutions used for diagnostic testing.

Investigated diseases

Blomia tropicalis allergy - Blomia tropicalis allergy is an allergic reaction caused by exposure to the dust mite Blomia tropicalis. When the mite proteins contact the skin or are inhaled, the immune system produces antibodies that trigger symptoms such as itchy skin, sneezing, runny nose, or watery eyes. Repeated exposure can increase the size of skin wheals during testing and may lead to more frequent or intense symptoms. The condition typically develops gradually as sensitivity builds up over time. Symptoms may fluctuate with the amount of mite exposure in the environment.
Trial detailsLast updated 11 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2026-525639-18-00Protocol codeM608-SSP-091Estimated enrolment70 patientsSponsorInmunotek S.L.

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