Penicilium Chrysogenum (Pen ch) IgE

If your asthma is hard to control, your eyes itch whenever you go down to a basement, or your sinuses act up in one building and not another, a common indoor mold may be part of the story. Pen ch IgE (Penicillium chrysogenum immunoglobulin E) is the allergy antibody your immune system makes against that mold, and a blood test can tell you whether you have it.

In people with moderate to severe asthma, sensitization to this mold, Aspergillus, or both goes along with weaker lung function and more damage on lung scans. A positive result can give you a specific trigger to look for, which is easier to act on than a vague sense that something in the air bothers you.

What This Antibody Is

Immunoglobulin E is the class of antibody behind allergic reactions. Immune cells called B cells start making it after your body decides a harmless substance is worth fighting, in this case proteins from Penicillium chrysogenum spores. Once it exists, it sits on allergy cells and primes them to release histamine and other inflammatory chemicals the next time you inhale the mold.

This test measures how much of that mold-specific antibody is circulating in your blood, reported in kU/L. A positive result shows that your immune system is primed against the mold. That is sensitization, not a diagnosis of mold allergy. Whether the mold is causing your symptoms depends on whether those symptoms line up with exposure, so the number is one piece of evidence and your history is the other.

One of the mold's main allergens is a protein-cutting enzyme called Pen ch 13. In lab experiments with human airway lining cells, it broke down the seals between cells and triggered the release of inflammatory signals, which suggests a way it could irritate the airways. Similar enzymes exist in other molds, which matters when you read a panel with several molds positive at once.

Because this is the mold species famous for producing penicillin, people often assume a positive result means a penicillin allergy. It doesn't. The test reflects your reaction to mold you breathe in, and allergy to the drug is checked with separate drug-specific testing.

Severe Asthma and Lung Damage

The strongest clinical case for this test is asthma that doesn't settle with standard treatment. In that group, sensitization to heat-tolerant molds tracks with lasting structural damage in the airways.

In a study of 431 adults with asthma, people sensitized to Aspergillus fumigatus, Penicillium chrysogenum, or both could blow out about ten percentage points less of their expected air volume after using a reliever inhaler (73.0% vs 82.8% predicted). Their chest scans showed more damage too: 54.5% had bronchiectasis, and 37.5% had areas of collapsed or consolidated lung. That study grouped the two molds together, and the authors found Aspergillus sensitization carried much of the association.

Bronchiectasis is permanent widening and scarring of the airways, which makes infections and mucus buildup more likely. It's the kind of damage that is far easier to prevent than to reverse.

What this means for you: if you have asthma that keeps flaring despite treatment and this result is positive, get lung function testing, and if it's reduced, have a lung specialist review a chest CT. Finding damage early changes how aggressively it's treated.

Allergic Bronchopulmonary Aspergillosis

Allergic bronchopulmonary aspergillosis is a condition in which the immune system overreacts to mold growing inside the airways, causing mucus plugs, inflammation, and over time bronchiectasis. When molds other than Aspergillus drive it, it's called allergic bronchopulmonary mycosis.

In one Guangzhou study of people already sensitized to Aspergillus, Penicillium chrysogenum IgE was also positive in 94.44% of those with allergic bronchopulmonary aspergillosis and 77.78% of those with Aspergillus-sensitized asthma without the full disease.

A positive result here is never enough for the diagnosis by itself. The diagnosis rests on a combination of findings, including a markedly raised total IgE, sensitization to Aspergillus, and characteristic changes on imaging, so this test works as a flag that says the rest of that workup is worth doing.

Allergic Conjunctivitis

Eye allergy is a less obvious place this mold group shows up. A small study measured serum IgE against Penicillium extract by ELISA, a related but not identical measurement. About one in five people with allergic conjunctivitis had Penicillium IgE (22.5%), compared with one in twenty healthy controls (5%). Higher antibody classes went with more severe eye findings.

The same study found that IgG, a different antibody type that builds up with repeated exposure, matched skin test results even more closely than IgE did. It's a small, single-center study, and mold IgG testing isn't used to diagnose mold allergy. What it does suggest is that a negative IgE blood result doesn't fully settle whether mold is involved in chronic eye irritation.

Age, Sex, and Who Tends to Test Positive

Across 1,651,203 people tested at a large US laboratory, 10.7% had IgE against this mold. Positivity was higher in males and peaked in the teenage years, and it was more common in people with asthma or eczema.

Age seems to cut both ways. Among 137 allergic children, sensitization to molds as a group peaked around age 7.7 to 7.8 and then declined. Among 212 people with asthma, IgE against the Pen ch 13 enzyme rose steadily with age, from 7% of those under 10 to 42% of those over 70.

Those two findings measure different things in different people, which is why they don't conflict. The childhood study used whole mold extracts in allergic children generally, while the asthma study used a research blotting method to look at a single mold protein in people with ongoing airway disease. The likely picture is that many children outgrow broad mold sensitization, while people with persistent asthma keep picking up sensitization to specific mold proteins through years of exposure, as the asthma study's authors proposed. Either way, your age shifts how likely a positive result is, so read the number alongside your symptoms and history.

Molds Travel in Groups

Molds share proteins, so IgE made against one species often binds another. The protein-cutting enzymes in Penicillium and Aspergillus are a well-known example. In the Guangzhou Aspergillus-sensitized asthma group, 87.04% were also positive to at least one other fungal allergen.

In a large analysis of US test results, apparent sensitization to several fungi was mostly explained by sensitization to one species plus cross-reaction with its relatives. So a positive result for this mold alongside Aspergillus, Alternaria, or Cladosporium may reflect one underlying sensitization showing up several times. Component testing measures IgE against individual mold proteins. It can help separate a true primary sensitization from a cross-reaction when the answer would change treatment.

What This Test Doesn't Predict

There's no evidence linking this antibody to heart attacks, cancer, or early death. The closest data come from 14,849 Danish adults followed for a median of 11.3 years, in whom having IgE against any inhaled allergen made no real difference to overall death rates (hazard ratio 1.03), deaths from heart and circulatory disease, or deaths from cancer. This test is about your airways, sinuses, and eyes.

When Results Can Be Misleading

Most of the ways this result goes wrong come from the testing itself, since mold allergy testing is less standardized than testing for pollen or dust mites.

• Lab and platform differences: in proficiency surveys, results from different commercial allergen IgE assays disagreed by more than 20% in 80% of measurements, and mold extracts, including those from this species, vary in content from batch to batch. Compare results run by the same lab on the same platform.
• Results near the cutoff: low-level results close to the lab's decision point are where labs most often disagree on whether a sample is positive or negative, so treat a borderline result as uncertain until it's repeated.
• Blood versus skin testing: among 168 people evaluated for mold allergy, skin prick testing found sensitization in 90 and blood testing in 56, so blood testing alone caught about 62% of what skin testing found. A negative blood result doesn't rule out mold allergy if your symptoms fit.
• Very high total IgE: when total IgE is extremely high, low-level specific IgE results can appear positive from nonspecific binding. Checking total IgE helps interpret an unexpected weak positive.
• Anti-IgE medication: omalizumab (Xolair) binds circulating IgE and lowers free IgE by about 89% to 99%. A result drawn while you're on it can read lower even though your underlying sensitization hasn't gone away.

Tracking Your Trend

IgE comes from long-lived antibody-producing cells, so it changes slowly and can persist for years after an exposure ends. A single reading tells you about your sensitization history more than about this week's air.

Repeated readings can help when the question is narrow. No one has measured how much this mold-specific antibody naturally drifts within a person, but total IgE (a related but different measurement) varied by a median of only about 2% between two draws a month apart in people with stable asthma. If that stability carries over, a clear rise in your result on the same lab's platform is more likely a real change in exposure or biology than noise.

Get a baseline. Retest when the result would change a decision: after a major move, after mold cleanup, after starting immunotherapy, or if breathing, sinus, or eye symptoms change. If you start allergen immunotherapy, the number may rise first and fall slowly over years, so judge it by the long-run direction.

What to Do With an Unexpected Result

• Positive, with symptoms that fit: look for dampness, visible mold, or musty smells at home and work, check the related molds (Aspergillus, Alternaria, Cladosporium) and total IgE, and see an allergist about reducing exposure and whether immunotherapy makes sense for you.
• Positive, with hard-to-control asthma: add total IgE, Aspergillus IgE, a blood eosinophil count, and lung function testing. A high eosinophil count goes along with scan abnormalities in fungal-sensitized asthma, and the combination of a markedly raised total IgE, Aspergillus sensitization, and high eosinophils calls for a pulmonologist to check for allergic bronchopulmonary aspergillosis.
• Positive, with no symptoms: this is common and isn't treated on its own. Keep it as a baseline, note which molds you react to, and retest if breathing, sinus, or eye symptoms appear.
• Negative, with strong symptoms around mold: ask an allergist for skin prick testing, which picks up mold sensitization more often than blood tests, and test the other common molds before ruling mold out.