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Wise et al.
Page 129
Mixing.: If multiple-allergen mixtures are to be used for SCIT, there are several considerations, in addition to ensuring that each extract in the mixture is at a concentration that will provide an effective dose when delivered with the maintenance injection. These considerations are (1) avoiding mixing extracts with strong proteolytic activity with extracts whose allergens are susceptible to this activity; (2) paying attention to allergenic cross reactivity; and (3) using preservatives that are appropriate for the allergens. 1632 All fungal and some insect body extracts (but not U.S. HDM extracts) have strong proteolytic activity to which many pollen, mite, and animal dander allergens are susceptible. 1639 Fungal and cockroach extracts should not be mixed, but fungal extracts can be combined. 1640 Plant pollens contain some allergens that are like the allergens of unrelated plants (pan allergens) but generally the major allergens are unique. When the appropriate allergens are available in the testing panel, the use of molecular diagnosis or CRD can be of great use in differentiating cross-reactivity due to pan-allergens from that due to multiple related major allergens. (See section VIII.F.6. Evaluation and diagnosis - In vitro testing - Component resolved diagnosis (CRD) for additional information on this topic.) When the patient is sensitized to the major allergens of botanically related plants there are 2 approaches that can be employed. 1641 One approach is to only include the locally most important member of a related group (such as ragweed or northern pasture grasses); the other approach is to use a mixtures of related allergen extracts, but treating it as if it were 1 allergen. 1641 Diluents.: Diluents containing 50% glycerin are excellent at maintaining extract potency and are used in the United States routinely for extracts with high protease activity. 1639,1642 The drawback to using extracts with high glycerin content is that they cause pain when injected. 1633 A phenol-saline extract containing 0.3% human serum albumin is well tolerated and, in the absence of high proteolytic activity, is an excellent diluent that may be used routinely for making dilutions for initiation of SCIT in the United States. 1643 Regimens.: For reasons of safety, SCIT is initiated at a dilution of the final dose and built up usually with weekly injections of increasing amounts and concentrations over a period of weeks or even months. Once maintenance doses are achieved, the interval between injections can be increased but usually not beyond 4 weeks with aqueous extracts used in the United States, 1623 but up to 4 to 6 weeks for depot extracts as used in Europe. 1614 Venue for administering SCIT.: SCIT in allergy practices in the United States is associated with a rate of severe systemic reactions of 0.1%. 1644 For this reason the Immunotherapy Practice Parameters 3rd Update state that injections should be given only in a medical facility where prompt recognition and treatment of anaphylaxis is assured and patients should remain under observation for at least 30 minutes following the injection. 1623 This is in line with the European perspective. 32 There is a company in the United States that promotes the practice of home administration of SCIT. 1645 Their protocol calls for administration of relatively low doses of SCIT several times per week resulting in a cumulative dose that approaches that recommended in the Practice Parameters. However, there is evidence to suggest that it is the size of the individual dose rather than the
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Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.
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