What is pH?
pH is a measure of the hydrogen ion concentration in a water solution. The hydrogen ion concentration indicates how acid or alkaline a solution is.
Numbers below 7 indicate an acidic solution - the lower the number the stronger the acid nature. Numbers above 7 indicate an alkaline or basic solution
- the higher the number the stronger the alkaline nature. Seven is neutral - distilled water not exposed to air being an example.
PH of the Skin
pH values for the skin are usually quoted in a 4.5 to 6.0 range. A value of 5.5 is the most common single value mentioned. The skin is said to have an
acid mantle -- a thin layer partly comprised of sebum and sweat where this value is measured. The acid nature of the mantle appears to retard certain
bacteria growth.
"Balancing Skin pH"
Some cosmetic products are quite alkaline -- hand soap has a pH of 9 - 10. Some cosmetic products claim to balance or adjust the skin's pH. What does this
mean? Hopefully this means keeping the pH in the skin's natural range. Making the skin more pH neutral is probably not a good idea. Furthermore, trying
to change the skin's pH from its natural range is futile as it will tend to restore to that range in time. But, formulating a product so that it lies
within the skin's pH range would seem reasonable as long as the ingredients used to do so are not irritating. But one must keep in mind that the pH of a
product "drifts" over time. That is, the pH on the date of manufacture may be quite different from a product that is still on the store shelf 90 days later.
pH of Sunless Tanning Solutions
What pH range should a sunless tanning solution be formulated to? DHA in solution occurs in an equilibrium state with glyceraldehyde. The more acidic
the solution, the more DHA occurs and less glyceraldehyde. The more basic the solution, the more glyceraldehyde and less DHA. At ph values above 7,
undesirable reactions occur that may compromise the product. When stored, DHA solutions will drift over time to a pH of 3 - 4, a range where the product
is particularly stable. For a DHA solution, it would appear best to formulate it to its natural pH range for both stability and effectiveness. So, we
would recommend you be more focused about the pH range of an aftercare moisturizer than the DHA solution.
Pre-Sunless Spritzes
Some pre-sunless spray products are sold to remove excess skin oils and grime when applied before a sunless tan. Such products are most valuable in
circumstances where the client has not exfoliated. Some of these products also claim to adjust the skin pH. We believe this to be a relatively minor claim.
Such products should be evaluated mostly on their ability to prepare a clean surface for sunless tanning product application.
pH of Some Common Substances
What are some common substances with a pH close to the value for healthy skin? Coffee and tea are two examples with a pH of about 5.0. Water exposed
to air is another. While distilled water is neutral at 7.0, water exposed to air will dissolve carbon dioxide to form a weak carbonic acid, ph of about
5.5. So, taking a bath where the tub is partially filled with the air and water mix from the shower may be good for skin pH. Acid rain is formed in a similar
manner - except that rain water has dissolved industrial gases to form more potent acids than carbonic acid. Seawater has a pH of about 7.7 - 8.3, so it
is partially alkaline. Seawaters are absorbing more CO2, the culprit in global warming. While this mitigates the level of CO2 in the atmosphere, the
increasing acidity of ocean waters may be very damaging to some sea creatures – impacting shellfish calcification and coral reef formation.
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