Thursday, December 9, 2010

Moisturizer alcohol burn bad; acid moisturizer good

Voov had another dermatology appointment today. Nothing urgent; just a checkup to see how she's doing on her restricted diet. The new development is that we are not to apply steroids unless she's having a significant flare. Hidden B has, it turns out, been putting Derma-Smoothe on Voov every second night (Hidden B and I trade kid duties on alternate nights) and every morning. "I can't tell what's a significant flare," she says. "They all look significant to me."

I, on the other hand, don't think Voov's skin has been bad for quite some time. So, on my shifts, I haven't been putting any Derma-Smoothe on. This is what happens even in a two-doctorate family: we don't know exactly what we're supposed to be doing with our kid.

I mentioned that recently I got suckered into buying some generic moisturizing "creme" at CVS. It sits right next to the Eucerin, comes in the same kind of jar, and costs half as much. Why do I have to learn this lesson over and over again? The CVS creme sucks. It's slippery and actually burns my skin, although the ingredient list is virtually identical to Eucerin's. (Not perfectly identical, though, and I'd guess that the CVS version has more alcohol.)

Anyway, Hidden B found Eucerin on sale at Target and got me two jars. So I chucked out the CVS stuff. Burn begone.

This month's Journal of Allergy and Clinical Immunology has an article you'd find interesting. (Editor's summary here.) Let me recap it for you.

Two amino acids that naturally occur on normal human skin can slow the growth and reduce the infectious potential of the bacterial pathogen Staphylococcus aureus, a group of Irish scientists have shown in laboratory experiments.  

S. aureus colonizes the skin of 5% of people without eczema, and 90% of people with eczema; it infects broken skin and secretes molecules that cause and prolong inflammation.

Normal skin controls S. aureus with antimicrobial agents and an acidic pH (about pH 5.5, compared to normal cellular pH of about 7.4). I am not sure what acids are responsible for this low pH; however, two products of the breakdown of the molecule filaggrin (see here and here), "UCA" and "PCA," are amino acid components of "natural moisturizing factor" known to hydrate the skin and possibly contribute to its acidity.

The scientists explored whether UCA and PCA could, in a test tube, inhibit the growth of S. aureus. The answer was yes. UCA and PCA also reduced bacterial production of proteins necessary for S. aureus to colonize skin and evade the immune system. The interesting thing is that the scientists found the same inhibitory effects when they used hydrochloric acid instead of UCA and PCA. So the acidity of amino acids, rather than some other chemical property, is responsible for much of the bacteria-controlling effect.

However, there is one area in which UCA and PCA appear to have special properties: they greatly reduce bacterial production of one iron-sensing protein that helps S. aureus stick to skin cells. Hydrochloric acid does not do this.

If anything from this research might prove useful in the future to eczema patients, it would be that chemists might consider adding UCA and PCA to moisturizers to provide antibacterial control. There is evidence (referenced in the paper) that acidic moisturizers help suppress S. aureus.

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