DIY Remedy - Minimize mark that a blemish may leave by mixing teaspoon baking soda and teaspoon distilled water to create a paste. Apply to affected area for 5 minutes, splash off. After, use cotton swab to dab on hydrogen peroxide.
Before century, all leavened bread was sourdoughbread, since they thought it was the yeast giving the bread the sour taste. Today we are able to produce yeast without lactobacillus which actually gives the sour taste.