Biological Standardization of Dermatophagoides Pteronyssinus Allergen Extract

Inclusion Criteria: * Subject has provided written informed consent, appropriately signed and dated by the subject (or legal representative, if applicable). * Subject can be male or female of any race and ethnic group. * Age \> and =18 years and \< and =60 years at the study inclusion day. * Medical history of allergy with respiratory symptoms (rhinitis and /or rhinoconjunctivitis and/or asthma) to Dermatophagoides pteronyssinus. * Positive skin prick test with a standardized commercially available preparation of Dermatophagoides pteronyssinus allergen extract. The skin prick test will be considered positive if the test results in a wheal major diameter of at least 3 mm or an area at least 7 mm2. Positive skin prick test results are valid if performed within one year prior to the inclusion of the subject in the study * A positive test for specific IgE to Dermatophagoides pteronyssinus (CAP-RAST major or equal to 2). IgE results are valid if performed within one year prior to the inclusion of the subject in the study. Exclusion Criteria: * Immunotherapy in the past 5 years with a Dermatophagoides pteronyssinus allergen extract or other mites allergen extracts known to interfere with the allergen to be tested, due to a high degree of cross-reactivity. * Use of drugs that may interfere with the skin reactions (e.g., antihistamines). See Appendix 1 of the protocol. * Treatment with any of the following medications: oral tricyclic or tetracyclic antidepressants or IMAOs, beta-blockers, chronic use of corticosteroids or use of oral or parenteral corticosteroids in repeated and intermittent patterns (10 mg/daily of prednisone or equivalent). * Women who are pregnant or period of breastfeeding and women with a pregnancy test positive during the visit 2, prior to the prick test. * Dermographism affecting the skin area at the test site at either study visit. * Atopic dermatitis affecting the skin area at the test site at either study visit. * Urticaria affecting the skin area at the test site at either study visit. * Diseases of the immune system relevant clinically, both autoimmune and immunodeficiencies. * Serious diseases not controlled that may increase the risk for the safety of the subjects involved in this study, including, but not limited to the following: heart failure, uncontrolled or severe respiratory diseases,endocrine diseases, clinically relevant kidney or liver diseases or hematological diseases. * Participation in any other clinical trial within 30 days (or 5 times the biological half-life of the research of the study product, whichever is longer) prior to the inclusion of the subject in this clinical trial. * Patients with diseases or conditions that limit the use of adrenaline (heart disease, severe hypertension...) * Severe psychiatric, psychological or neurological disorders * Abuse of alcohol, drugs or medicines in the previous year.