Titration of immunotherapy by periodical nasal allergic challenges in the treatment of allergic rhinitis

Objective To determine the benefits of nasal allergen challenge (NAC) in monitoring immunotherapy for allergic rhinitis in a clinical setting. Design Two hundred consecutive courses of immunotherapy, with pyridine‐extracted alum‐precipitated allergen extracts (Allpyral), were personally carried out by the writer and analysed. Diagnosis before treatment was confirmed by NAC and the duration of treatment determined by periodical NAC. Setting Consultant allergist's clinical practice. Participants Patients with allergic rhinitis who were referred for treatment; 79 patients were allergic to grass, 70 to the house dust mite, 30 to plantain and 21 to miscellaneous allergens. Results The mean protein nitrogen units (pnu) required to reverse an NAC was 145 467 pnu for grass, 93 771 pnu for mite, 103 137 pnu for plantain, and 121 030 pnu for miscellaneous allergen patients. The range of injections to obtain conversion to a negative NAC was wide. For grass it was 9–58 injections, for mite 6–47 injections, for plantain 4–39 injections, and for miscellaneous allergens 10–79 injections. Ten grass‐sensitive patients who received an average of 477 807 pnu failed to convert to a negative NAC result. Similarly, two mite‐sensitive patients who received 467 370 PNU, and one plantain‐sensitive patient, one cat‐sensitive patient and one horse‐sensitive patient, who had 389 240 pnu, 148 520 pnu and 719 540 pnu respectively, failed to convert. One patient who was very sensitive to grass pollen developed urticaria which required an injection of adrenaline. Conclusion Immunotherapy for allergic rhinitis with Allpyral is effective — as determined by the conversion of NAC results from positive to negative — providing a sufficient dose is given. The manufacturer's recommended dose is inadequate. The procedure is safe for mite, plantain and miscellaneous allergens, and only one reaction occurred with grass given in a high dosage protocol, which has subsequently been altered. Considering that the British Committee of Safety of Medicines reported no deaths from Allpyral injections, its recommendations appear over cautious for this make of extract.