European House Dust Mite (Der p 23) IgE Test · Blood

If you have year-round congestion, asthma flares, or eczema that never fully clears, dust mites are one of the most common culprits. But not all mite allergies look the same on a lab report. A subset of people react mainly to a single mite protein called Der p 23 (Dermatophagoides pteronyssinus allergen 23), and standard extract-based tests can underrepresent it because this protein binds tightly to mite fecal pellets and releases poorly into the liquid used in conventional assays.

This test measures Der p 23 specific IgE (immunoglobulin E, the antibody class that drives allergic reactions) in your blood. A positive result tells you that your immune system has built antibodies aimed at this particular mite protein, which is linked to asthma, allergic rhinitis, and atopic dermatitis. It also helps explain mite-related symptoms when broader mite tests come back unclear.

What Der p 23 Is and Why It Stands Out

Der p 23 is one of the major allergens produced by the European house dust mite. It originates in the mite's gut and ends up on the outside of its fecal pellets, which become airborne when household dust is disturbed. Once inhaled, the protein can trigger a Th2-driven allergic immune response (a type of immune reaction that drives allergies), prompting B cells to produce IgE antibodies aimed specifically at Der p 23.

Among house dust mite allergic patients, Der p 23 sensitization is common. Large European and Italian cohorts find it in roughly 56 to 66 percent of mite allergic patients, with mean IgE levels generally lower than the levels seen for the better-known mite proteins Der p 1 and Der p 2. In severe atopic dermatitis with a strong Th2 pattern, prevalence climbs as high as 97.5 percent.

Asthma Risk

Children sensitized to Der p 23 carry a higher risk of asthma than children without it. In a German birth cohort, early Der p 23 IgE (appearing by age 5) predicted school-age asthma and mite-related rhinitis. Asthmatic children with mite allergy show a wider IgE response to multiple mite proteins and higher specific IgE levels than non-asthmatic atopic children.

Levels also track with how controlled the asthma is. In a study of children in East China, lower Der p 23 IgE was associated with better asthma control, while higher levels appeared in partially controlled or uncontrolled disease.

Allergic Rhinitis

Der p 23 is one of the top mite proteins driving year-round nasal allergy. In a large Italian multicenter study of 519 mite allergic patients, about 60 percent had IgE to Der p 23, and roughly 8 percent were sensitized only to this protein. In some cases, IgE to Der p 23 exceeded the IgE level measured against the whole mite extract, which is the test most allergy clinics still use first.

Adding Der p 23 to a panel of Der p 1 and Der p 2 only modestly increases detection in many populations, but in a meaningful minority it identifies real mite allergy that would otherwise be missed.

Atopic Dermatitis

Mite allergy often plays a hidden role in stubborn eczema. In a high-exposure subtropical cohort of severe atopic dermatitis patients with mite sensitization, 97.5 percent had IgE to Der p 23, and higher titers were seen in more severe disease and in the Th2-high atopic dermatitis pattern. In adults with severe atopic dermatitis treated with the biologic dupilumab for 52 weeks, blood IgE to Der p 23 fell significantly.

What a Positive Result Actually Means

A detectable level of Der p 23 IgE means your immune system has built antibodies that recognize this specific mite protein. The higher the level, the broader and more active your mite-driven allergic response is likely to be, and the more likely you are to have asthma, rhinitis, or atopic dermatitis driven by mites. A negative result does not rule out mite allergy. Some people are sensitized only to Der p 1, Der p 2, or other minor mite proteins, so this test is most informative when interpreted alongside other mite components.

Why One Reading Is Not Enough

IgE levels are not fixed. Der p 23 sensitization patterns shift across the life course, with prevalence climbing in childhood, peaking in late childhood, and gradually declining toward adulthood. In one large Italian dataset, prevalence dropped from 73 percent in the youngest patients to 35 percent in the oldest. A single number captures one moment in a moving picture.

Tracking your level over time tells you more than any single value. If you are starting allergen avoidance, immunotherapy, or a biologic medication, retest in 6 to 12 months to see whether your immune system is shifting. Beyond that, an annual check builds a personal trend line. In studies of subcutaneous and sublingual immunotherapy, changes in Der p 23 related antibodies show up within months and continue to evolve over years.

When Results Can Be Misleading

• Assay differences: different labs use different platforms (ImmunoCAP, microarrays, chemiluminescence). Numbers between platforms are not always interchangeable, so trend with the same lab when possible.
• Extract-based comparisons: standard whole mite IgE tests can underrepresent Der p 23 because the protein binds tightly to mite fecal pellets and releases poorly into the test extract. A normal whole mite IgE does not always mean Der p 23 IgE is also normal.
• Age effects: Der p 23 IgE is more common in children and younger adults, and prevalence falls with age. A lower level in an older adult may not mean your overall mite reactivity is lower.
• Threshold sensitivity: Der p 23 IgE levels tend to be lower than Der p 1 or Der p 2, which can put results close to the positivity cutoff. Borderline values are best confirmed with repeat testing.

What to Do With an Out of Pattern Result

A positive Der p 23 IgE on its own is a starting point, not a verdict. Pair it with the rest of the mite picture: Der p 1, Der p 2, and ideally a broader component panel (Der p 5, 7, 10, 21) plus a total IgE to put the result in context. If your standard mite extract or skin prick test is negative but Der p 23 is positive and your symptoms fit, this is one of the situations the component test was designed for, and it strengthens the case for an allergy and immunology workup.

If you have moderate to severe symptoms, especially asthma, persistent rhinitis, or atopic dermatitis, a result that confirms mite sensitization should prompt a conversation with an allergist about environmental control measures and whether you are a candidate for allergen immunotherapy. In a large phase III sublingual immunotherapy tablet trial, Der p 23 status did not change clinical efficacy, meaning standard mite immunotherapy still works whether or not you are sensitized to this specific protein.

The Bigger Picture

Der p 23 sits in the middle of a broader shift in allergy diagnostics: from testing for whole extracts to testing for the specific molecules that drive your symptoms. It will not replace standard mite IgE or skin prick tests for most people, but it can clarify ambiguous cases, refine risk assessment in children with early signs of allergic disease, and add precision when you are weighing immunotherapy options.