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Symptoms induced in pollen challenge chamber similar to seasonal allergies

Symptoms elicited through allergen exposure in a pollen challenge chamber were concordant with those resulting from seasonal allergies in a recent study.

Thirty-one participants in San Antonio sensitive to ragweed recorded their symptoms during a 15-day period in giant ragweed season. Twenty-six of these responders were then exposed to short ragweed pollen in a pollen challenge chamber (PCC) for three hours daily for up to four days. Researchers hypothesized that a strong correlation exists between allergic symptoms received from in-season, natural exposure to giant ragweed and those received from out-of-season exposure to short ragweed in a PCC.

During the natural phase, the mean total ocular system score (TOSS), total nasal system score (TNSS) and total system score (TSS) results were 4.4, 8.4 and 11.8, respectively. Most participants (84%) had a TOSS greater than 5 and a TNSS of 7 or greater on four consecutive days.

Among those who participated in the PCC phase, 14 completed the full four days, while the remaining 12 dropped out, primarily because of heightened symptoms. The 14 participants were considered slow/low responders, and those who exited early were labeled rapid/high responders.

The mean TSS on the first day was 5.16 after 30 minutes, with an intercept increase of 1.78 by day 4 (P=.005), and the overall TSS per minute increased by 0.015 during the four days (P=.026). Slower responders experienced rapid TSS increases on the fourth day, while rapid responders experienced progressively faster increases after each PCC visit. The increase in symptom levels was comparable to that experienced by participants during natural pollen exposure.

Correlations in scores between the natural and PCC exposures were 0.57 for TOSS (P=.002), 0.56 for TNSS (P=.002) and 0.65 for TSS (P=.0002). Several symptoms also were significantly correlated between the two exposures, including tears (P<.003), eye redness (P<.004), nasal itch (P<.0004) and nasal congestion (P<.001).

“Our findings affirm our hypothesis, underscore the high cross-reactivity between distinct pollens, and highlight the utility of the PCC to identify novel allergy endotypes that might have contrasting mechanistic underpinnings and potentially therapeutic responses,” the researchers wrote, adding that the results also suggest the potential usefulness of using multiple, geographically dispersed PCCs containing a single allergen in phase III clinical trials.