CD16 Medical-grade manuka honey and a sugar-free manuka honey extract inhibit allergic IgE-induced mast-cell degranulation: potential role as an topical anti-inflammatory agent in atopic dermatitis

Mast-cell numbers and activity are both increased in atopic dermatitis (AD) lesions. AD is characterized by allergen–IgE–FcεRI-induced mast-cell activation, associated with allergic responses to specific types of foods or allergens. Medihoney® (MH) is a medical-grade manuka honey with strong antimicrobial properties. Recent reports also suggest it has anti-inflammatory properties via inhibition of histamine release by mast cells. In the present study, we investigated the anti-inflammatory effect of MH and a sugar-free manuka honey extract (EX) against allergic inflammation by studying its effect on mast-cell degranulation induced by IgE. LAD-2 human mast cells were preincubated overnight with 100 ng mL−1 of human myeloma IgE, then activated by 1% antihuman IgE for 40 min with or without 20-min preincubation with 4%, 2% and 1% of MH or EX. Degranulation was assessed by measuring release of the lysosomal enzyme β-hexosaminidase. Both MH and EX induced significant dose-dependent inhibition of IgE-induced mast-cell degranulation, culminating at 85% and 100% inhibition, respectively, at 4% concentration. In conclusion, MH and EX potentially inhibit allergic IgE-induced mast-cell degranulation. Aqueous preparations of MH and EX (applied topically) could potentially be useful as anti-inflammatory agents directed against the allergic inflammation involved in the pathophysiology of AD.