Repeated latex aeroallergen challenges employing a hooded exposure chamber: safety and reproducibility

Background: Bronchial, nasal, and conjunctival challenges are useful for clarifying discordant clinical history (Hx) and skin and/or serologic tests and in assessing semiquantitative changes in biologic sensitivity over time. The objective of this study was to determine the safety and reproducibility of repeated latex‐allergen challenges with a hooded exposure chamber (HEC). Methods: The HEC system comprises a powered forced‐air respirator with a fitted face shield and hood that uses glove‐derived latex‐allergen associated cornstarch particles (LAC) to expose simultaneously the conjunctiva, nose, and lungs. Serial control and incremental LAC challenges are conducted until an endpoint based on upper and/or lower respiratory tract symptoms and peak expiratory flow rates is reached. Six latex‐allergic (Hx and puncture skin test [PST]‐ and 5/6 radioallergosorbent test [RAST]‐positive) subjects were challenged on three separate occasions at least 2 weeks apart. Serial latex PST midpoints and serum anti‐latex IgE by RAST were monitored at each visit and at a fourth follow‐up visit. Results: All subjects responded to LAC, but not to air or control cornstarch administered as controls. All responses were confined to mild symptoms of allergic rhinoconjunctivitis and/or asthma that either resolved spontaneously or were reversed with inhaled albuterol. No subject experienced a systemic or delayed reaction. There were no significant changes in the endpoint LAC doses over the three challenge visits (P>0.2). The mean coefficient of variation for log2 endpoints within‐subjects was 17.3±17.2% (SD). The serum latex‐specific IgE was not significantly boosted by the three challenges (P>0.2). The concentration of latex extract necessary to produce an 8‐mm wheal by PST was not significantly changed during the study (P>0.1), indicating that latex sensitivity was not affected by the repeated LAC exposures. Conclusions: The results of this study indicate that repeated HEC latex‐allergen challenges are both reproducible and safe, and do not increase latex sensitivity.