Biological Standardization of D. Glomerata, L. Perenne, S. Cereale and O. Europaea Pollen Extracts

Inclusion Criteria: A. Subjects sensitized to one or more allergen extracts: 1. Positive clinical history with inhalant allergy to at least one of the allergen to be standardized. 2. At least one positive prick test (mean wheal diameter greater or equal than 3mm) . 3. Positive prick test (wheal diameter greater or equal to 3 mm) to Histamine 10 mg/ml 4. Age: 18-60 years 5. Written informed consent 6. Patients will preferably be monosensitized, or with clinically relevant sensitization , or with primary sensitization (maximum cutaneous reactivity) to the extracts under investigation. 7. Women of child-bearing potential must have a negative urine pregnancy test at the time they begin the study. B. Atopic Subjects: 1. Age: 18-60 years 2. Written informed consent 3. Positive prick test (wheal diameter greater or equal to 3 mm) to Histamine 10 mg/ml 4. Negative prick test (mean wheal diameter less or equal to 3mm) when tested with already standardized extracts of the allergens under investigation or with cross reactive extracts. 5. Women of child-bearing potential must have a negative urine pregnancy test at the time they begin the study. C. No Atopic Subjects: 1. Age: 18-60 years. 2. Written informed consent 3. Positive prick test (wheal diameter greater or equal to 3 mm) to Histamine 10 mg/ml 4. Negative prick test (mean wheal diameter less or equal to 3mm)to all allergens tested in diagnostic prick test. 5. Women of child-bearing potential must have a negative urine pregnancy test at the time they begin the study. Exclusion Criteria (shared by the 3 groups): 1. Immunotherapy in the 2 years prior to the study against either the allergen to be tested or an allergen which is cross-reactive. (it is not applicable to no atopic patients) 2. Any drug which may interfere with the cutaneous test or with its result. 3. Any medical condition that from investigator's point of view the skin prick test cannot be done . 4. Women who are pregnant or breast-feeding or are child-bearing age and who have not demonstrated that they have been surgically sterilized or have other means of not bearing children. 4.Subjects who have participated in another clinical trial within 3 months prior to this study.