Nasal and skin sensitivity during immunotherapy with two major allergens 19, 25 and partially purified extract of timothy grass pollen.

In a double blind 3-year prospective study 40 grass pollen allergic patients were allocated to specific immunotherapy (hyposensitization) with two timothy major allergens, 19, 25, or partially purified timothy extract. The extracts were biologically standardized and coupled to aluminium hydroxide for treatment. Efficacy of hyposensitization was evaluated by titrated nasal provocations and skin prick tests with the two treatment extracts and a five-gram mixture. The threshold dose for skin prick test (skin thresholds) produced reactions identical to histamine chloride 5.43 mmol/l and the threshold dose for nasal provocations (nasal thresholds) produced two of the three reactions: at least 0.5 ml of nasal secretion, at least five sneezes, and/or at least a 20% fall in nasal peak flow. Nasal thresholds showed highest efficacy from partially purified timothy extract but equal protection against timothy and the five-grass mixture. Nasal thresholds of 14 untreated patients corresponded to treatment with the two major allergens. Changes in skin and nasal thresholds after 12 and after 54 weeks of treatment predicted the severity of hay fever. Increase in nasal thresholds coincided with a marked effect on asthma. Nasal thresholds below 1 HEP before treatment predicted major systemic side effects.