Why is the pH of soap so important?

Soap Why does the pH or soap matter? (Image: PNGFind)

India is in the midst of a war, a great soap war between German soap maker Sebamed and FMCG giant Hindustan Unilever. All hell broke loose after the former brought out a cheeky ad, alleging that HUL’s premium soap brand Dove may not be as mild as it claims it is. On the pH spectrum, Dove ranks at 7 while Sebamed sits pretty at 5. The ad obviously had HUL frothing at the mouth, dragging Sebamed to court over the “disparaging” advertisement.

As a connoisseur of drama in any form, I have been enjoying watching a well-known FMCG bully (look up HUL’s transgressions) getting a$$ whopped by the underdog Sebamed. But it also made me wonder — “What’s the big deal anyway? Why is the pH of soaps so important?”

What is pH?

pH stands for Potential of Hydrogen, which is a spectrum or a scale used to determine whether something is acidic or alkaline.

The human body, to keep up its healthy state, maintains an acid-base balance.

In the absence of illnesses, the pH of the human body is between 7.35 to 7.40, which is ideal for our biological processes. Under 7.35, the body becomes acidic. Above 7.44, it becomes too alkaline.

Each organ in the body relies on the pH balance, including the human skin. The skin surface is slightly acidic with an “acid mantle” covering the stratum corneum or the upper layer.

Hand sanitizer: Why I hate it and you should too!

ph scale
pH scale (Image: Canva)

Why the pH of soap is important

If your skin is healthy, the pH is around 5.4-5.9 with normal bacterial flora.

Any kind of disturbance in the balance may cause acne, irritant contact dermatitis, atopic dermatitis, ichthyosis and Candida albicans infection. That’s because the acid mantle maintains the beneficial bacterial flora of the skin.

But studies show that the skin pH increases in proportion to the pH of cleansers. That’s why, cleansers should ideally have a pH of 5.5, which is closest to the skin’s pH, to prevent skin diseases.

In other words, soaps and facewashes should be slightly tilting towards acidity.

But most companies don’t provide the pH of their cleansing products on the labels.

The importance (and joy) of making your bed in the morning

A 2014 study published in the Indian Journal of Dermatology evaluated samples of commonly used soaps and shampoos. The samples were then tested using a pH meter.

Shockingly, the majority of the soaps tested had a pH between the range of 9 and 10. Shampoos were in the range of 6-7. Only 3.1% of the soap samples had safe pH levels.

Even some products that were promoted as anti-acne cleansers had pH above 9. That’s scary since Propionibacterium —┬áthe culprit responsible for acne — can increase with the use of alkaline soaps.

How can you test your soap’s pH?

Forget what Sebamed or HUL says. You can find out whether your favourite brand of soap is lying or not with simple home tests.

Litmus paper is the most inexpensive and accurate method of testing pH at home. All you have to do is place a strip on the soap and wait for it to change colour.

Each kit comes with a colour scale, red and warmer shades representing acidity and blue and cooler shades indicating alkalinity. Place the litmus paper against the scale to see where the colour fits.

pH scale
pH scale (Image: Wikimedia Commons)

Purple or red cabbage juice has a water-based pigment, which can be used as a pH indicator. Squeeze the juice out of the cabbage and place a few drops on the soap you want to test.

If the juice turns blue, your soap is (supposedly) in the safe pH limits. Instead, if it turns green or yellow, you can safely discard it.

If you are particularly brave, you can try the taste test too (at your own risk). Touch the soap with the tip of your tongue. If the taste feels like an electric jolt, it means there’s too much lye in it and its alkaline.