2007 ICD-9-CM Procedure 99.12 Immunization for allergy Immunosuppression by the administration of increasing doses of antigen. Though the exact mechanism is not clear, the therapy results in an increase in serum levels of allergen-specific IMMUNOGLOBULIN G, suppression of specific IgE, and an increase in suppressor T-cell activity. Treatment or therapy to reduce or eliminate a patient's allergic response to an allergen (NCI/OSP) 99.12 is a specific code that can be used to specify a procedure 99.12 contains 2 index entries View the full Volume 3 99.* hierarchy 99.12 also known as: Desensitization Index entries containing 99.12: Desensitization allergy 99.12 Immunization -- see also Vaccination allergy 99.12