pH balance of skin

What is pH?

It refers “potential of hydrogen” in water solution. The scale of pH runs from  0-14.

pH<7: Acidic

pH7: Neutral

pH>7: Alkaline

What is the optimal pH value of skin?

Most of our face and body lies on pH4.70 - pH5.75 (mildly acidic). Men’s skin tends to be more acidic than women’s skin. When the skin is getting old, it becomes more acidic.

Why does pH of skin need to be balanced?

When the pH of skin is disturbed by external conditions like temperature, humidity, chemical exposure, pollution or skin care products, skin barrier compromises to balance skin pH. If the process keeps repeating, skin's barrier turns to be less resilient, more sensitive, drier that can trigger breakouts, signs of eczema, redness and sensitivity.

Highly acidic (pH 2.5 or lower) or alkaline (pH 8 or greater) products can cause more significant disruption in skin’s pH, so it takes skin longer to get back to normal.

Do I need to use the pH balanced product?

Recommend pH for skin care products is pH 4.0-7.0. However, when the cosmetic chemists formulate products, they also consider effective pH value of each ingredients in the products. For example,

Ascorbic acid (vitamin C): stable and effective @ pH 2.6-3.2

AHA(Glycolic Acid, Lactic Acid, Malic acid, Tartaric acid)/ BHA(Salicylic Acid): stable and effective @ pH 3.0-4.0

Sunscreens with Zinc Oxide: stable and effective @ pH 7.0-8.0

Can I layer skin care products with different pH levels?

Yes, as long as their pH values are similar, but too much products may cause peeling because thick multiple layers can't be absorbed into skin but just stay on the surface of the skin.

If the pH values are too different (too acidic+too alkaline), they can conflict each other. Not only making each other less effective but also causing peeling if the polymers used in alkaline products are not compatible with acidic condition.

If you want to layer too acidic+too alkaline products, wait for a while to let the first product be absorbed before you use the second product. Or you can use one in the morning, and the other one at night.

References

International Journal of Cosmetic Science, October 2006, pages 359-370
Skin Pharmacology and Physiology, July 2006, pages 296-301