The pH value of adult skin in their faces and bodies ranges between 4.7 to 5.75. The best skincare products are made with a pH value of 5.5, although, a range of 4.5 to 7 is the most common. Any value above or below that will cause irritation to the skin. The further the pH value goes from the optimal range, the more irritation it will cause. At the extremes values of 1 and 14, your skin will suffer from severe burns.