Assessment of Residual Allergenicity of Tree (Birch, Hazel, and Alder) Pollen Allergoid Using Skin Prick Testing

Inclusion Criteria: * The subject must sign the study consent form prior to any screening procedures being performed. * If the volunteer is female of childbearing potential, she must demonstrate a negative urine pregnancy test and agree to remain abstinent or use an effective method of birth control or use a hormonal contraceptive * The subject must demonstrate a positive skin prick test to Birch, Hazel and Alder pollen allergen extract * The subject must demonstrate a positive skin prick test to positive histamine control * The subject must demonstrate a negative skin prick test to negative control * The subject must demonstrate a specific IgE for Birch, Hazel and Alder as documented by a RAST (radioallergosorbent test), or equivalent test * The subject must have clinically acceptable results from the screening procedure. Exclusion Criteria: * History or presence of acute or subacute atopic dermatitis, chronic dermatitis, urticaria factitia, or urticaria due to physical/chemical influence or any other skin conditions which might interfere with the interpretation of skin prick test results * Visual inspection of the forearms indicates potential problems with the conduct or interpretation of the skin prick tests; both forearms must be available for testing * Subject has asthma or other lower respiratory tract condition * History or presence of diabetes, cancer or any clinically significant cardiac, metabolic, renal, hepatic, gastrointestinal, dermatologic, venereal, hematologic, neurologic or psychiatric diseases or disorders * Any clinically significant abnormal laboratory value at Visit 1 * Clinically relevant sensitivity to any common perennial allergen: house dust mites, molds, epithelia (cat, dog, and horse), grass mix * Clinically relevant symptoms due to an IgE - mediated allergy at screening and before inclusion to the treatment period. * Secondary alteration at the affected organ. * History of auto-immune diseases or rheumatoid diseases * Subject has a medical condition that prohibits the use of adrenalin * Subject has disorder of tyrosine metabolism * Subject with diseases interfering with the immune response and have received medication, which could influence the results of this study * Subject has acute or chronic infection * History of anaphylaxis * History of angioedema * Subjects determined by the Investigator to have any medical condition that could jeopardize their health or prejudice the results * History of hypersensitivity to the excipients of the study medication * History of immunotherapy with tree allergen extracts * Current therapy with ß-blockers * Currently receiving anti-allergy medication or other drugs with antihistaminic activity * Subject has a positive drugs of abuse screen at Visit 1 * Subject participated in a clinical trial with an investigational drug within the last 30 days * Subject cannot communicate reliably with the Investigator or is deemed uncooperative or noncompliant * Females who are pregnant, breastfeeding, or refuse to use a reliable method of birth control * Subject received treatment with a preparation containing MPL during the past 12 months * Use of prohibited medications or inadequate washout periods prior to screening