Since the time J. had eczema herpeticatum he is having recurring bacterial infections (staphylococcus aureus) on his skin. Those are small puss filled pustules mainly on the upper legs and lower arms. The infection usually flairs up when he is sick (cold, cough) and often comes with some fever. It probably didn’t help that we had to treat him with antibiotics twice this fall (when he had eczema herpeticatum which came with a bacterial super-infection, and later an ear infection), which surely disturbed his bacterial skin population. And of course it doesn’t help that J. is opening the pustules when scratching.
Thanks to a small side note by Spanish Key on one of his recent blog posts I realized that there is a connection between the altered pH value of eczema skin and bacterial infection (I didn’t know that!). We found this nice review article  summarizing the pH value of the skin and its impact on the skin’s barrier function. According to this article and the cited literature, the low pH value (acidic) is important for the regulation of enzyme activity, that is responsible for the laminar structure in the stratum corneum (the outer layer of the skin) that forms the skin barrier, which we need for a healthy skin. A high pH value (close to neural) is associated with a disturbance of that barrier, and consequently the pH value is much higher on affected skin areas of eczema patients than on healthy skin. There seems to be a progressive increase of pH value from the skin of healthy children to healthy skin of eczema children to affected skin of eczema children. What makes matters worse, most microbes prefer a pH value close to neutral, and as Spanish Key pointed out in his blog, the bacterium staphylococcus aureus prefers the higher pH value of eczema skin. And when the colonization and bacterial growth gets out of control (e.g. due to a weakened immune system) then the skin becomes infected. Interestingly, every washing of the skin raises the pH value temporarily. Using conventional alkaline soap will rise the pH value of the skin for several hours, and even using clear water or acidic soap, will raise the pH value temporarily. But because the more acidic the soap the smaller and shorter is the raise of the pH value of the skin, the recommendation of the authors is to use acidic soap as a prevention of bacterial infections.
I bought pH testing strips and I am now testing every cream and lotion and soap…..
 Schmid-Wendtner, MH, Korting, HC (2006). The pH of the skin surface and its impact on the barrier function. Skin Pharmacol Physiol, 19, 6:296-302.