xRead - September 2022

Wise et al.

Page 66

• Harm: The additional risks, including systemic or anaphylactic reactions, of intradermal tests; additional time and discomfort. • Cost: Similar to intradermal testing. • Benefits-Harm Assessment: Benefit outweighs harm. • Value Judgments: AIT can be initiated from SPT results alone; however, endpoint-based AIT may decrease time to reaching therapeutic dose. • Policy Level: Option. • Intervention: MQT is a skin testing technique that may be used to determine a starting point for AIT. VIII.E.4. Issues that affect the performance or interpretation of skin tests VIII.E.4.a. Medications.: The wheal and flare reaction seen in allergy skin testing depends upon the physiologic actions of histamine released from mast cells upon degranulation. Thus, any medications that inhibit mast cell degranulation or that function as histamine H 1 receptor antagonists have the potential to suppress appropriate skin test responses. The suppressive effects of H 1 antihistamines on allergen and histamine induced wheal and flare responses vary greatly, 863,864 and the duration of this suppression depends upon the skin tissue concentration and half-life of these agents. 865,866 In fact, skin test suppression can be used as a biological assay for the onset and duration of action of antihistamines. 865 Agents such as astemizole (now removed from the market due to QT prolongation) have the potential to suppress skin test reactions for a period of weeks after cessation. 867 However, most antihistamines only suppress skin test responses for a period of 2 to 7 days after cessation. 867,868 Topically administered antihistamines have the potential to suppress skin wheal and flare responses. One randomized placebo-controlled study showed that 14 days of azelastine nasal spray treatment reduced the histamine induced wheal and flare response, and this suppression disappeared by 48 hours after cessation 869 (Table VIII.E.4.a-1). Randomized, placebo-controlled trials have demonstrated that H 2 receptor antagonists such as ranitidine can reduce skin whealing responses, 870,871 and 1 study showed an additive effect of H 1 and H 2 antihistamines on skin wheal suppression. 872 Some antidepressants have the potential to suppress skin wheal and flare responses, in particular the tricyclic antidepressants that have antihistaminic properties (such as doxepin). 873 However, newer classes of antidepressants such as selective serotonin reuptake inhibitors (SSRI) do not appear to affect allergy skin test responses. 874 Recombinant humanized anti-IgE monoclonal antibody (mAb), omalizumab, interferes with IgE-mediated mast cell degranulation reactions in the allergy skin test response. A randomized placebo-controlled trial demonstrated a significant reduction in allergen-induced skin whealing after 4 months of treatment. 874 Omalizumab appears to suppress skin test reactivity in tandem with dramatic reductions in serum free IgE, and allergy skin test responses return to normal within 8 weeks of discontinuation. 875

Author Manuscript Author Manuscript Author Manuscript Author Manuscript

Int Forum Allergy Rhinol . Author manuscript; available in PMC 2020 June 10.