Quick, pop quiz time. Riddle me this: What does primary school chemistry and perfectly porcelain complexion have in common? Answer: pH value.

Now, surely you’ll have some nebulous notion of “pH value” – kids the world over will recall many an afternoon spent amusing themselves with pH test strips – but what does “the concentration of hydrogen ions in a substance” (yup, cribbed that definition off of my cousin’s textbook) have to do with the state of our skin?

Elementary, my dear. You see, our skin’s surface is actually acidic in nature, hovering between the 5.4 to 5.9 on the pH scale. (By way of comparison, good ol’ H20 is naturally neutral at the midway seven-point mark; acutely acidic or alkaline stuff are a searing zero and 14 respectively.)  

Here’s the intriguing implication: If you’re in the habit of marinating your mien in products that are excessively alkaline – think soapy suds and traditional toners – you’re actually whittling away at the protective mechanism of your skin’s “acid mantle” (derm-speak for the outer film that fends off environmental aggressors like the sun and smog.)

Indeed, your face fares best when it’s slightly “sour”, so to speak; experts even suggest that an acidic pH value can play a part in preventing pimples and enlarged pores. “You need some acidity to inhibit bacterial growth on the skin,” says Howard Sobel, MD, dermatologist and director of the New York Institute of Aesthetic Dermatology and Laser Surgery. “which is why skin that’s too alkaline may, for example, be more susceptible to acne.”

Want more? There’s also evidence pointing to a connection between alkalinity and an aged appearance; a watershed study found that women with alkaline skin were more likely to have creases and crinkles in their complexion than their more acidic counterparts.

What this means for you, my beauty buddy, is this: Stray too far south of the magical 5.5 pH value and you might just find your skin becoming wrinkly and wracked with pimples and pores.

All of this can sound more than a little scary, but the solution is simple, really: Steer clear of old-school soap – that uncomfortably stretched and squeaky sensation is a dead giveaway of excessive alkalinity – and make for milder milk or mousse cleansers instead. (Several beauty brands also proffer pH-balanced products; decent drugstore options include Sebamed, Simple and Hada Labo, just to name-drop a few.)

Bottomline: For baby-soft skin, switch to soap-free solvents, which are less likely to cause the skin irritation which can boil over into blemishes and fine lines, and cap your cleansing to twice a day. Here’s to passing the “acid test”, pretty people!

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