Ågren compared two occlusive zinc oxide dressings: a commercial gum-rosin adhesive with 25% zinc oxide, and a hydrocolloid made for the study with 6% zinc oxide. They were tested on intact human forearm skin and on full-thickness rat wounds. On intact skin, zinc in epidermis and blister fluid was about twice as high under the rosin vehicle. On wounds the ranking reversed, and both zinc oxide dressings raised serum and liver zinc well above the control. The paper concludes that the vehicle is “an important determining factor for Zn delivery through intact and to wounded skin”.
Key numbers
Table I (human, 48 h, n=5): epidermal zinc was 49 ± 5 µg/g dry weight under the 6% hydrocolloid and 127 ± 26 µg/g under the 25% rosin dressing (p<0.05). Blister-fluid zinc was 0.29 ± 0.04 and 0.68 ± 0.10 µg/ml (n=4, p<0.05). Individual subjects ranged from 36 to 61 and from 92 to 217 µg/g. A plain hydrocolloid in one subject gave blister-fluid zinc of 0.49 µg/ml, compared with 0.45 µg/ml under the zinc oxide hydrocolloid. The author reads this as no percutaneous absorption from the hydrocolloid.
Table II (rats, 24 h after wounding, n=5 per group, mean ± SEM): serum zinc was 0.95 ± 0.02 µg/ml (plain hydrocolloid control), 4.06 ± 0.48 (6% zinc oxide hydrocolloid) and 2.56 ± 0.20 (25% rosin dressing). Liver zinc was 146 ± 2, 390 ± 23 and 206 ± 11 µg/g dry weight. In vitro, zinc oxide dissolved to 67 µg/ml with hydrocolloid and 28 µg/ml without, in buffered saline at pH 7.4.
The introduction cites earlier rat work in which labelled zinc from the rosin dressing on wounds gave blood activity about 100-fold higher than on the same area of intact skin.
Methods (brief)
Human arm: two 8 cm2 dressings per volunteer for 48 h, 10 tape strippings, then suction blisters. The blister roof (epidermis) and fluid were analysed. Rats: two 10 cm2 full-thickness excisions, dressings for 24 h, then serum and liver. Zinc was measured by atomic absorption spectrometry and compared by t-test.
Evidence fitness
The paper supports two findings: zinc from zinc oxide reaches the viable epidermis of intact adult skin under occlusion, and full-thickness wounds allow much greater systemic uptake. It is relevant to diaper dermatitis with erosion only by analogy, because the vehicles are dressings. It measures zinc, not the lead or cadmium carried in zinc oxide.
Limitations
The groups are very small. The recomputed SEM for the rosin-dressing epidermis mean is 22.9, where the table prints 26. The Table II footnote prints the same threshold (p<0.01) for two significance symbols. The 25% dressing is stated as 2.7 mg Zn/cm2 and the 6% dressing as 6.0 mg Zn/cm2, so the lower percentage carries more zinc per area. Layer thickness is not given. The OCR text layer mislabels Table II as Table I. The page image is used.
Related evidence
- Diaper Cream, ZnO-Based
- Zinc
- Early Intervention by a Ward Pharmacist for the Hyperzincemia Caused by Zinc Oxide Ointment in a Infant with Diaper Dermatitis: A Case Report
- Human Epidermal Zinc Concentrations after Topical Application of ZnO Nanoparticles in Sunscreens
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