Minerals and the Skin
7.2 Zinc
7.2.3 Impact on the Skin
Many skin disorders have been associated and treated with zinc (e.g., dandruff, acne, diaper rash), and oral zinc therapy has been shown to be effective in treating inflammatory conditions (Schwartz et al. 2005). Success rates for treatment with zinc vary depending on the disease, mode of application, and zinc salt used (Nitzan and Cohen 2006).
7.2.3.1 Zinc and Skin Appearance
Zinc has been shown to protect the skin cell membrane. A negative correlation was observed between zinc intake and skin evenness as well as the hydration of facial areas. However, as it is thought that the activity of the antioxidant enzymes, rather than the serum mineral concentration, has a positive influence on the moisture content of the facial areas excessive zinc intake is not recommended for skin mois- turizing (Bae et al. 2010).
7.2.3.2 Zinc in the Healing Wound
For more than 3,000 years, orally supplemented or topically applied zinc in the form of zinc oxide or calamine has been used in the treatment of skin wounds. Admittedly, it is still unclear how much additional zinc a wound needs for the healing process to be enhanced or to what extent topical applied zinc is absorbed. After more than 100 published reports, the precise role of supplementary zinc therapy remains unclear (Lansdown 1996), but observations show that the requirement for zinc in the skin is higher during the process of healing (Henzel et al. 1970; Schwartz et al. 2005); and in individuals with dietary zinc deficiency or hereditary hypozincemia, zinc therapy is indicated for wound healing (Lansdown 1996).
Not only is zinc a constituent of enzymes that play a central role in reconstruction of a wound’s matrix (Henzel et al. 1970), it also plays a significant role in the extra- cellular matrix, cell migration, protein synthesis, and modulation of inflammatory cytokines such as decreasing production of tumor necrosis factor-a (TNFa) (Bowe and Shalita 2008). In addition, zinc has an effect on the expression of integrins, which are cell surface proteins that mediate interactions between the cell and the various extracellular matrix proteins surrounding it. The effect of zinc was particularly
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notable on these integrins, affecting cellular mobility during the proliferative phase of wound healing (Schwartz et al. 2005).
7.2.3.3 Zinc and Acne
As patients with acne were reported to have low levels of serum zinc (Fitzherbert 1977), acne itself seems to be a symptom of zinc deficiency. It may be due to over- production of male hormones, which was observed in cases of zinc deficiency. Used both internally and topically, zinc works to clear the skin by reducing oil production and may be effective in controlling the formation of acne lesions or help those already present to heal quicker by its antiinflammatory effect (Bowe and Shalita 2008).
During the 1970s, evidence was provided that acne improved with oral zinc supplementation in zinc-deficient patients (Fitzherbert 1977; Michaëlsson et al.
1977). Subsequently, trials showed that orally taken zinc was effective in the treatment of severe and inflammatory acne—more so than mild or moderate acne.
Although these trials did not control for other dietary factors, oral zinc salt supple- mentation has been shown to be equal to or less effective than oral tetracyclines.
However, the oral doses of zinc used in most of these studies (zinc gluconate 200 mg/
day, zinc sulfate 400 or 600 mg/day) were associated with nausea, vomiting, abdominal cramps, and diarrhea (Bowe and Shalita 2008; Fitzherbert 1977; Michaëlsson et al.
1977; Rebello et al. 1986).
7.2.3.4 Zinc and Psoriasis
To which extent zinc is involved in the pathogenesis of psoriasis is not yet clear, but it seems that oral zinc supplementation has no effect on the skin manifestation of psoriasis (Burrows et al. 1994), although it ameliorates conditions of psoriatic arthropathy (Frigo et al. 1989; Clemmensen et al. 1980).
7.2.3.5 Zinc and Hair Loss
There is a widespread belief that zinc deficiency can cause hair loss in humans, which is seen only with severe zinc deficiency (Sherertz and Goldsmith 1991).
However, there is no evidence of a link between low serum zinc to chronic telogen effluvium (CTE) (Arnaud et al. 1995) or alopecia areata (Ead 1981).
7.2.3.6 Zinc and Herpes Simplex Infections
Some studies indicate that oral zinc treatment may be considered as part of overall immune-enhancing therapy for patients with recurrent herpes simplex infections, leading to a reduction in attack frequency as well as a reduction in the duration and severity of outbreaks (Gaby 2006).
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7.2.3.7 Topically Applied Zinc Diaper Dermatitis
Zinc oxide, often combined with castor oil, has a special place in the treatment of diaper dermatitis (diaper rash). Although the ointments are often thought to be primarily a barrier cream separating the skin from the irritating excreted matter, it is likely that the antiinflammatory and antimicrobial activity of zinc oxide can help alleviate the symptoms (Schwartz et al. 2005; Scheinfeld et al. 2006).
Dandruff
Zinc pyrithione is an antifungal agent that is effective as an antidandruff agent and for seborrheic dermatitis (Bissett 2009). Zinc itself may also have an impact beyond the antifungal action: The antiinflammatory effect may reduce hyperproliferation of the dandruff skin (Schwartz et al. 2005). Moreover, zinc inhibits the enzyme responsible for converting testosterone to its biologically active metabolite, which mediates most of the actions typically ascribed to androgenic hormones, including stimulation of sebaceous gland activity (Sugimoto et al. 1995; Stamatiadis et al.
1988). Thus, reduction of sebum secretion is known to result from zinc exposure (Demetree et al. 1980) and could be an additional benefit of the use of zinc-containing antidandruff treatments (Schwartz et al. 2005).
Acne
With regard to acne, topically applied zinc has been proven to have positive effects due to its antimicrobial and antiinflammatory effects as well as reduction of hyperproliferation and high sebum production. Zinc is bacteriostatic against Propionibacterium acnes, one of the bacteria involved in causing acne. Zinc inhibits chemotaxis (Bowe and Shalita 2008) and may also directly inhibit bacterial lipases from converting sebum triglycerides to fatty acids, which are presumably more potent mediators of acne (Rebello et al. 1986). A combination of an antibiotic with a soluble zinc salt has resulted in decreased sebum production, as shown in clinical studies (Piérard-Franchimont et al. 1995). Comparison of the zinc-containing antibiotic treatment with one without zinc (although also at a lower antibiotic level) demonstrated the zinc-containing product to have greater lesion reduction efficacy (Habbema et al. 1989).
Herpes Simplex Skin Infections
Topically applied zinc preparations can shorten the duration of herpes simplex skin infections and possibly prevent recurrences. Although most studies used zinc sul- fate, zinc monoglycerolate or zinc oxide-glycine may also be beneficial. Zinc oxide,
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however, seems not to be effective because it does not release a sufficient amount of zinc ions to exert an antiviral effect (Gaby 2006).