Suppression of Immediate and Late Anti-IgE-Induced Skin Reactions by Topically Applied Alcohol/Onion Extract

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Abstract
In a double blind study, alcohol/onion extract (5% ethanol) was injected simultaneously with 20 and 200 IU rabbit anti-human-IgE intradermally in 12 adult volunteers (6 atopics, 6 non-atopics). Diameters of wheals and flares were measured 10 min after and compared with control sites challenged with 20 and 200 IU anti-IgE in a 5% ethanol solution. Skin sites were then treated epidermally with 45% alcohol/onion extract and 45% ethanol under occlusion. Diameters of late cutaneous reactions were measured hourly. Edema formation was clinically estimated according to an arbitrary scale and skin thickness measured with a calliper. In the onion-treated skin sites the wheal areas were significantly reduced (20 IU: control: 108 .+-. 53 mm2; onion 69 .+-. 42 mm2, P < 0.05; 200 IU anti-IgE: control 152 .+-. 25 mm2, onion: 138 .+-. 26 mm2, P < 0.02). Edema formation during the late phase skin reaction was markedly depressed (P < 0.005 at 2 h, P < 0.01 at 4 and 6 h, P < 0.02 at 8 h). The extent of late skin reactions was slightly but not significantly reduced. Obviously, onions contained pharmacologically active substances with anti-inflammatory and/or allergic properties.