Standardising Nasal Allergen Challenge in Adult With Hay Fever

Nasal allergen challenge (NAC) is a useful tool in the investigation of allergic rhinitis, including grass pollen‐induced seasonal allergic rhinitis (hay fever). We have experience in using NAC to investigate the clinical and immunological effects of allergen exposure and in using NAC as a surrogate outcome to assess the efficacy of treatments for allergic rhinitis. The procedure is safe and well tolerated. In order for NAC to be a valid tool, it is essential that the allergen extracts used are standardised in terms of concentration and stability in solution. We have previously used an extract of Timothy Grass (Phleum pratense) pollen, Aquagen (ALK‐Abello, Denmark). Aquagen is supplied as a dry powder, to be reconstituted prior to use by dissolving in an albumin‐based diluent. Unfortunately, Aquagen production has been discontinued, but the identical allergen is now available as Timothy Grass lyophilisate tablet, Grazax (ALK‐Abello), an approved and licensed product for treatment of severe seasonal allergic rhinitis. Grazax consists of purified, freeze‐dried Timothy Grass pollen extract, plus only three excipients, gelatin (from fish), mannitol and sodium hydroxide. Preliminary investigations have shown that Grazax tablets can be dissolved in saline to produce identical concentrations of allergen to Aquagen, with the same stability profile in vitro. We anticipate therefore, that the clinical effect when used for nasal allergen challenges would be equivalent to the use of Aquagen for a given allergen concentration. In this study we intend to confirm that nasal symptoms produced during the NAC with either Aquagen or Grazax will be equivalent. We will recruit volunteers with grass pollen‐induced hay fever to undergo NAC with each allergen source, sequentially. In an open, randomised‐order, cross‐over study. The primary outcome will be patient‐reported nasal symptoms (according to a standardised scoring system) in the 60 minutes after each nasal challenge.