How is pigmented skin more acidic?

 How is Pigmented Skin More Acidic?   As we discussed in an earlier post, darkly pigmented skin is superior to lightly pigmented skin. It functions better in holding in body water. It does a better job of preventing skin infections. And it is better at resisting mechanical trauma.  We then discussed work from the Elias laboratory demonstrating that this superiority is due to the lower pH of the skin surface.  In other words, darkly pigmented skin is more acidic. Yet darkly pigmented … [Read more...]

Our Sour Skin Surface

Did you know that the surface of our skin is acidic? That we have a sour skin surface, like vinegar or lemon juice?  Scientists have long known that we are covered by an acid mantle. But how the epidermis - the outer layers of skin - achieves this feat, conferring a pH of 5.0 or less to our skin surface, when the cells of our body and the blood and fluids bathing those cells have a more neutral pH of ~7.4, has until recently been something of a mystery.   To our surprise, as we were … [Read more...]

Black Skin Is Better

This proposition - that black skin is better skin - is not a political statement. Rather, it is based upon scientific observations. Darkly pigmented skin is functionally superior to lighter colored skin in several ways. Our purpose here is give our readers a scientific perspective to a socially fraught question. And to acquaint our readers with some of the most important functions of skin that are influenced by skin color. Some of the benefits of skin color are obvious and widely … [Read more...]

Highlights of the 2013 IID. Part 6: Does barrier repair therapy improve skin defense against infection?

Prior work from our group has shown that the permeability and antimicrobial barriers in normal skin share many common features, and are co-regulated, such that perturbations in one function inevitably impact the other. We also showed that a variety of conditions that compromise the permeability barrier, including neonatal and aging skin, are also accompanied by a reduction in the production of the cathelicidin antimicrobial peptide, LL-37, a key defender against S. Aureus and Streptococcal … [Read more...]

HIghlights of the IID 2013. Part 4: The Good Side of Psychological Stress

It is widely held that the stress of our modern lives is bad for our health. And it is certainly true that stress (or, more precisely, 'psychological stress') can be harmful to the function of our skin. It delays wound healing. It can reduce our immune defenses against infection.  And, as we demonstrated several years ago, it can compromise the skin’s permeability barrier. It is also accepted by many that stress exacerbates chronic inflammatory diseases, like rheumatic disorders and inflammatory … [Read more...]

HIghlights of the IID. Part 3: How Melanin Is Good For The Skin Barrier

In previous work, we demonstrated that the skin of darkly-pigmented people possesses a tighter, more competent barrier to water leakage than does the skin of lightly-pigmented individuals.  Although we could attribute this to the much more acidic (lower pH) skin surface in individuals with dark pigmentation, just how either melanin or its parent cell, the melanocyte, confers these benefits was unknown. For the studies reported here, we took advantage of two closely related strains of hairless … [Read more...]

Highlights of the IID 2013. Part 1: Evolution and filaggrin mutations vs. vitamin D production

Did latitude-dependent differences in prevalence of filaggrin mutations evolve to support cutaneous vitamin D production? JP Thyssen and PM Elias. Skin became more lightly pigmented when modern humans migrated northward out of Africa into Europe and Asia. Evolutionary biologists increasingly accept the hypothesis that pigmentation lightened in order to allow more ultraviolet light to enter the skin, where it can then stimulate the formation of additional vitamin D. In a recent article in … [Read more...]

What Allows Our Skin Cells to Shed?

The epidermis is a self-renewing system. Old cells (or ‘squames’) are shed from the skin surface as new cells (‘keratinocytes’) are produced in the underlying epidermis and pushed outward into the stratum corneum to become 'corneocytes'. In normal skin, the process of desquamation is invisible and imperceptible.  But in some skin diseases, the production of cells may increase and/or the mechanism of shedding may be faulty, resulting in the visible build-up and eventual shedding of unsightly … [Read more...]

Thoughts on the Rational Treatment of Atopic Dermatitis

This is the 4th in our series of updates on atopic dermatitis. In the preceding articles we considered why so many more children nowadays are developing eczema, what we know about the genetic underpinings of the disease, and how defects in the skin barrier and loss of the acidic pH on the skin surface are key to understanding how the dermatitis develops. In this post we consider how this information provides the basis for new, rational paradigms for treatment. Migration back to life on … [Read more...]

Atopic Dermatitis: Is It All About pH?

In two earlier posts we discussed why atopic dermatitis is becoming more prevalent and what is known about the genetic underpinings of this common disorder. In this installment, we look at how the most common gene associated with atopic dermatitis acts to produce the skin condition. It has known for decades that the skin has a "sour surface". The pH of the skin surface is acidic (~5), while our cells and blood have a nearly neutral (~7.4) pH. This low surface pH is assumed to be critical to … [Read more...]

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