[The clinical significance of challenge tests (author's transl)]

108 pollen-sensitive persons (positive skin test, positive history) and 40 latent pollen-allergic persons (positive skin test, but no conjunctival or nasal manifestations during the flowering season) were given intranasally increasing concentrations of pollen extract until a reaction occurred (itching, sneezing, running and blocked nose). 7.4% of the patients reacted to 0.001% w/v of the pollen extract, 56.5% reacted to 0.01, and 36% to a dose of 0.1% w/v. The corresponding figures for persons with latent allergy were 0.7, 5 and 30%; 62.5% reacted to 1.0 or 2.5% w/v of the extract. There was a relatively sharp division between doses of 0.1 and 1.0% w/v: persons who responded only to 1% concentrations invariably belonged to the group of latent allergy. 35 persons with positive skin tests to dust mites were divided into 3 groups: those with either a positive or a negative history of dust allergy and those concentrations of dust mite extracts (0.012, 0.12 and 1.2% w/v). Patients were considered to have latent allergy if they were sensitive to dust mite but were free from symptoms; or if they were sensitive to dust mite and pollen, but were symptom-free outside the flowering season. Although the group reacted slightly more often only to concentrations of 1.2%, the nasal response occurred on the whole with the same frequency with all three concentrations. In contrast to pollen allergy a positive intranasal dust mite test is not necessarily clinically relevant. Provocation tests are, therefore, not an infallible means to ascertain the presence of clinically relevant allergy.