A revisit to the effects of zinc salt on skin burn wound healing to reflect the risks in current pharmaceutical care.

The lower limit of soluble zinc content that can possibly be applied onto a wounded skin as a healing promoter was not known. This study examined skin wound healing process of rats inflicted by partial thickness thermal burn wound as a function of applied soluble zinc contents (0.1 ml of zinc chloride solution 0.01% (w/w) or 5.0% (w/w)). The size, surface morphology and histological profiles of wound beds of untreated rats and those treated with zinc chloride solutions were characterized. A soluble zinc content as low as 10.5 μg/cm2 of skin negated skin wound healing when compared to the untreated rats. This was alarming as the commercial products currently in the market are formulated with a high level of zinc content. Albeit the zinc salt employed was water-insoluble, a minute fraction of soluble zinc might be available to the treatment sites. This could be partially responsible for the late adverse effects such as pruritis and inflammation reported with calamine/diphenhydramine lotion, medicated shampoo, Olay Complete defense moisturizing lotion and Zineryt® topical solution. The skin irritation was likely a resultant oxidative stress action of soluble zinc, where a small fraction could be adequate to negate the skin homeostasis.[Figure: see text]Key messagesZinc is essentially a cofactor for skin collagen formation.Soluble zinc content as low as 10.5 μg/cm2 of skin irritates skin and negates burn wound healing.Skin irritation of commercial products relates to minute soluble zinc content availability.