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If you have asthma, year-round nasal symptoms, or unexplained respiratory flare-ups indoors, mold sensitization may be part of the picture. Many basic allergy panels test only a handful of common molds, which means a real trigger can sit hidden in the data.
Stemphylium IgE checks one of those less commonly tested molds. Because Stemphylium shares its main allergen with Alternaria, a positive result also flags membership in a broader family of mold sensitivities that often travel together.
The test measures Stemphylium botryosum IgE, an immunoglobulin E antibody (a type of allergy antibody your immune system produces) that specifically recognizes proteins from this mold. IgE antibodies are made by B cells, a type of white blood cell, and they sit on mast cells throughout your airways and skin. When you breathe in a mold protein your IgE recognizes, the mast cells release histamine and other chemicals that drive allergy symptoms.
A positive result means your body has produced antibodies against Stemphylium and is technically sensitized. Sensitization is not the same as a clinical allergy. Some people with detectable IgE never develop symptoms, while others react strongly. Your symptom history, exposure pattern, and the size of the antibody response together determine whether the sensitization is clinically meaningful.
Stemphylium botryosum belongs to a fungal family called Pleosporaceae, which also includes Alternaria alternata and Ulocladium botrytis. These molds share a major allergenic protein called Alt a 1. In a Spanish study of mold-sensitized patients with rhinitis or asthma, an Alt a 1-like protein was detected in Stemphylium extract and was recognized by IgE in every sensitized patient tested.
What this means in practice: if you test positive for Stemphylium IgE, your immune system is likely reacting to allergens shared across this whole mold family, not just to Stemphylium itself. The same protein that triggers your response may exist in Alternaria growing in damp basements, on stored food, or on outdoor crops in late summer and fall.
Sensitization to molds in this family has been linked to allergic rhinitis (year-round or seasonal nasal symptoms) and asthma. In a study of asthmatic children, an extended mold testing panel that included Stemphylium identified additional patients with mold-specific IgE that a smaller standard panel had missed. Stemphylium was useful for flagging children with sensitization to seven or more different molds, a pattern associated with more difficult-to-control respiratory disease.
Sensitization to the broader Alternaria-related family has also been associated with more severe asthma in the published literature. The clinical takeaway: a clearly positive Stemphylium IgE in someone with respiratory symptoms is worth investigating, especially if a standard mold panel did not turn up an obvious trigger.
These cutpoints come from the standard ImmunoCAP-style specific IgE assay used by most reference laboratories. They are general orientation, not strict diagnostic targets. Cross-reactivity within the Pleosporaceae family means a low-positive Stemphylium result may primarily reflect sensitization to Alternaria, so always interpret your number alongside other mold IgE results and your symptoms.
| Class | Range (kU/L) | What It Suggests |
|---|---|---|
| Negative | Less than 0.10 | No detectable sensitization |
| Borderline | 0.10 to 0.34 | Very low antibody levels, clinical meaning uncertain |
| Class 1 | 0.35 to 0.69 | Low positive, possible sensitization |
| Class 2 | 0.70 to 3.49 | Moderate positive, sensitization likely |
| Class 3 and above | 3.50 or higher | Strong positive, sensitization clearly present |
Compare your results within the same lab over time for the most meaningful trend. Different assays and different labs can produce slightly different numbers from the same blood sample.
A single specific IgE reading is a snapshot. Levels can shift with seasonal exposure, recent illness, and the effect of any treatments. Tracking the trend matters more than fixating on one value, because a clear rise or fall over time tells you whether your immune system is becoming more reactive to this mold or settling down.
A reasonable cadence is to get a baseline now, retest in 3 to 6 months if you are pursuing remediation or starting allergen-targeted therapy, and then at least annually if you have respiratory symptoms or known mold exposure. If you live somewhere with a clear mold season, retesting at the same time of year removes one source of variability.
An isolated positive Stemphylium IgE in someone with no symptoms generally does not require treatment. The decision pathway changes when the result is paired with respiratory or skin symptoms.
Specific IgE detects sensitization, not symptomatic allergy. Many people have measurable antibodies without ever having a clinical reaction, which is one reason results should always be interpreted alongside symptoms and exposure history.
Evidence-backed interventions that affect your Stemphylium Botryosum Mold IgE level
Stemphylium Botryosum Mold IgE is best interpreted alongside these tests.