The flanks of hairless mice (n=4–5 each) were treated with topical applications of either diphenhydramine chlorhydrate (H1r), cimetidine (H2r), or ethanol (vehicle) twice-daily for four days (see Methods for further details). At the end of treatments, changes in basal barrier function, assessed as transepidermal water loss (TEWL, a), surface pH (b), and electrical conductance (SC hydration, c) were measured. (d) Barrier disruption was induced by sequential cellophane tape strippings until TEWL levels ≥ 10-fold increase over baseline, and barrier recovery rates were assessed two and four hrs later (a=p<0.05 vs. vehicle, b=p<0.01 vs. vehicle, c=p<0.001 vs. vehicle, and d=p<0.001 vs. H1r+H2r)66. e: Percent barrier recovery was compared in mast cell-deficient KitW/KitW-v double heterozygote mice (MCDM) vs. wild-type (WBB6F1) mice two and four hrs after tape stripping, as above.