The study is meant to establish a one-step challenge with grass-pollen in patients sensitized for grass-pollen. Therefore the investigators compare a multi-step challenge with grass-pollen with an one-step challenge in order to survey the repeatability and safety.

Background:

Specific provocation with inhaled allergens is an established tool in clinical practice and research, supporting the understanding of pathophysiology of allergic asthma, and analysing the efficacy of new therapies. This study examines the repeatability of a bolus-dose inhalative allergen challenge with grass pollen.

Method:

Forty grass pollen allergics should undergo an incremental-dose grass pollen challenge to calculate their PD20-dose. This calculated dose will be applicated twice to analyse the repeatability of the bolus dose challenge. Before and twenty-four hours after the provocation, exhaled nitric oxid (FeNO) will be determined as a marker of bronchial inflammation.

Inclusion Criteria:

• age >12 <45 years
• known sensitization for grass-pollen
• informed consent

Exclusion Criteria:

• age <12 >45 years
• clinical asthma requiring regular inhalation
• vital capacity <80%
• FEV1 < 75%
• chronic disease conditions or infections
• pregnancy
• inhalative or systemic steroid use
• substance abuse
• incapability of understanding the study's purpose and performance

Subjects undergo allergen challenges with incremental doses of grass pollen allergen. In those subjects, who develop a fall in FEV1 of more than 20%, this is followed by two single-step challenges in an interval of at least seven days.