Dandruff and Seborrheic Dermatitis Result from Scalp Barrier Breach and Irritation
Christina M. Gemmer, BS; Yvonne M. DeAngelis, CVT; Joseph R. Kaczvinsky, Ph.D.; James R. Schwartz, Ph.D.; Thomas L. Dawson, Jr, Ph.D.;
The etiology of dandruff and seborrheic dermatitis (D/SD) have become clearer over the last decade1. The skin physiology of D/SD is much more complex than a superficial flaking2. In this study, we define the role of Malassezia metabolism on scalp, investigating the role of irritating free fatty acids released by sebum digestion. We have also shown that removal of Malassezia, and hence the irritating metabolite, both corrects the pathophysiology (as demonstrated by electron microscopy) and improves the skin's barrier function (as demonstrated by a reduction in TEWL).
The objective of this study was to investigate the effect of oleic acid (OA), a sebum component3, on scalp condition as measured by ultrastructure, flaking, and barrier function. Comparison was also made between dandruff-susceptible and dandruff nonsusceptible individuals, to investigate the role of basal barrier function on the effect of OA.
Figure 1. Dandruff and seborrheic dermatitis (D/SD) are more than just superficial disorders of the stratum corneum, including parakeratosis, intracellular lipid droplets, decreased desmosomes, membrane inter-digitation, and excess intercellular lipid. The abnormality is normalized by pyrithione zinc (PtZ) shampoo2.
Figure 2. Topical application of oleic acid (OA) induces a dandruff-like desquamation in the absence of Malassezia fungi, but interestingly only in dandruff-susceptible individuals.
Figure 3. Removal of Malassezia (and hence their free fatty acid metabolites) with a PtZ containing shampoo improves barrier function as evidenced by decreasing TEWL.
(Insert figures here)
Here we report evidence for differences in the skin barrier's ability to prevent flaking induced by fatty acid application between dandruff-susceptible and nonsusceptible individuals.
- Oleic acid, a fatty acid component of human sebum3, is shown to induce a dandruff-like desquamation which is ultrastructurally identical to dandruff.
- The same dose of oleic acid does not induce flaking in subjects who are not predisposed dandruff.
- Removal of the insult significantly improves scalp health as measured by TEWL. The presence of abnormal SC across the scalp of D/SD sufferers1, along with the lower susceptibility to oleic acid induced flaking are further indication of an innate susceptibility in the skin of D/SD sufferers.
References1. AK Gupta, et al., Skin diseases associated with Malassezia species. JAAD 51:785-98. 2004 2. R. Warner et al.: Dandruff has an altered stratum corneum ultrastructure that is improved with zinc pyrithione shampoo. JAAD 45:897-903, 2001 3. VR Wheatley: The chemistry of sebum. in The physiology and pathophysiology of the skin, Volume 9, The sebaceous glands, A. Jarrett, ed., Academic Press, NY, NY, 1986 4. G Imokawa et al.: Decreased level of ceramides in stratum corneum of atopic dermatitis: An etiologic factor in atopic dry skin? JID 96:523-526, 1991