This does the opposite of what we need. If bedding tends to be the dust-mite location that most irritates allergy sufferers, we would expect a 69% reduction in mattress allergens to lead to a decrease in allergy symptoms. We want something that shows why that didn’t happen here.

Even if the allergy sufferers exaggerated the severity of their symptoms, they would have done so both before and after the study, meaning we would still expect the reports to show a change due to the decreased allergen exposure. This answer doesn’t explain why that didn’t occur.

In order for this to be the right answer, we would need some indication that the information the medical community is missing would explain why the allergy sufferers in the experiment did not experience a reduction in symptoms. Because this doesn’t give us that, it’s not helpful.

This explains why the participants in the study did not experience a reduction in their allergy symptoms: their exposure to allergens did not decrease enough to lead to symptom relief.

This doesn’t help us. Many studies are structured this way; as long as participants are unaware of which group they are in, we wouldn’t expect a placebo effect to skew the reports of allergy symptoms.