pH is the degree of hydrogen ion concentration in a substance or solution. It can also be defined as the unit of measure for acidity (or alkali/basic). Acidic means a higher concentration of hydrogen ions. Alkaline, therefore, is less concentration of hydrogen ions. The pH range goes from 0 to 14 with 0 being the most acidic and 14 most alkaline. Neutral would be pH 7.

pH can be determined by two common methods. One method is by using a flat glass electrode (pH meter). The glass probe on the end of the meter is placed in contact with a substance. The meter will then be able to give you a numeric reading of the pH level. The other method is with litmus paper (pH strips). This special paper, once saturated with a solution, is able to indicate through color coding the pH of a solution. Some strips can only indicate if it is acidic or alkaline. There are more accurate strips where a certain set of colors corresponds to a pH value.

Our skin surface has a pH. This pH is normally about 5.5. Our skin has a protective barrier called the acid mantle or hydrolipid film. Although, different parts of your body vary in pH level, healthy skin's protective barrier generally has a mildly acidic pH. In this environment, bacteria are less capable to survive. Disruption to the pH level can lead to dry, chapped, rough, or even irritated skin.

In order to provide a good perspective about pH and acidity, here are some values of common substances:

  • Wines ~ 2.8 – 3.8
  • Apples ~ 2.9 – 3.3
  • Orange Juice ~ 3.0
    • Oranges ~ 3.0 – 4.0
  • Grapefruit Juice ~ 3.0 – 3.3
  • Raspberries ~ 3.2 – 3.6
  • Grapes ~ 3.5 – 4.5
  • Tomato Juice ~ 4.0
    • Tomatoes ~ 4.0 – 4.4
  • Beers ~ 4.0 – 5.0
  • Bananas ~ 4.5 – 4.7
  • Pumpkin ~ 4.8 – 5.2
  • Carrots ~ 4.9 – 5.3
  • Blackberries ~ 4.9 – 5.5
  • Beans ~ 5.0 – 6.0
  • Asparagus ~ 5.4 – 5.8
  • Potatoes ~ 5.6 – 6.0
  • Normal rain ~ 5.7
  • Seawater ~ 8.0 – 9.0
  • Regular Soap ~ 9.0 – 10.0
  • Milk of Magnesia ~ 10.0
  • Household ammonia ~ 11
  • Household bleach ~ 12

(These are approximations)

General Chemistry by Brady and Humiston, 1986
pH simplified by Robert J. Joyce, Markson Science Inc.
pH and your skin by Audrey Kunin, MD, dermadoctor.com
What is pH 5.5?, sebamed.ca
pH Values for Common Items, jackeden.com
Food and Foodstuff pH Values, engineeringtoolbox.com
Measurement of Skin pH by S. Dikstein and A. Zlotogorski