By Allan Mak (see bio below)
If you’re reading this, then you must be asking yourself about your greasy scalp:
Why is my hair always greasy? OR
What causes oily hair all of a sudden?
Today, I want to talk to you about everything HAIR — about the chemistry of hair and how you can minimize dermatitis that takes the form of greasy scalp or waxy buildup on scalp and prevent further damage to your locks at the same time.
A few weeks ago, I was reading Jennifer’s post Waxy, Greasy Hair After Shower: A Surprising Form of Dermatitis, and it got me curious. Why does baking soda work for some people with dermatitis, but not others? I was particularly intrigued by one of the comments she got from one of her readers:
Jennifer, you need to stop telling people to use baking soda. Baking soda is VERY bad for the skin and disrupts the acid mantle barrier.
What is Acid-Mantle?
The scalp has a pH of 5.5, which is on the acidic side of the pH scale.  This acidic mantle (like a film) keeps out bad bacteria the surface of the skin. If our skin was a flower garden, then the acidity of the skin is our natural de-weeder. A breakdown of acidity causes bacteria to multiply, causing several issues including greasy scalp, oily hair, itchiness and discomfort.
ILW Recommends: If you suffer from dermatitis, psoriasis, or an itchy scalp and still cannot find relief, we suggest looking into an elimination diet to heal the body from the inside out.
According to dermatologists at the UCSF Medical Center, “…skin acidity has a protective role and discourages growth of many environmental bacteria and fungi…Studies have shown that washing with synthetic detergents of pH 7 increases the Propionobacteria acne count significantly compared to using a synthetic detergent with a pH of 5.5…Moreover, the lyphae form of candida, which is the initial invader to the skin, grows optimally at a pH above 6.5.” 
For this reason, most shampoos are usually formulated to have a lower pH than water, so that it is easier to maintain an acidic bacterial barrier. Here is a list of pH in common shampoos.
A fun fact: Child and pediatric shampoos are formulated to be closer to neutral – neither acidic or basic – marketed under the label of “no tear” shampoos.  Good on the eyes, but not so great on hair and usually full of chemicals.
Hair on the other hand is even more acidic than your scalp. It comes it at a swelteringly acidic pH level of 3.67. 
ILW Recommends: For a natural, effective and safe shampoo, take a look at our Emily Skin Soothers Natural Body Wash for Eczema with Chinese Herbs – it works very well as a shampoo!
Apple Cider Vinegar vs. Baking Soda
So back to that reader’s comment – let’s discuss the pH of apple cider vinegar and baking soda. Apple cider vinegar is composed of 5% acetic acid and has a pH of 2.8-3.0 , while baking soda has a pH of 9.5 .
Chemical and Physical Behavior of Human Hair reports that “hair displays a minimum swelling when it is at pH 2 to 9 with a slight increase in swelling below pH 2 and a considerable increase in swelling above pH 9 (using extended soaking times). Swelling causes the hair to be more susceptible to structural damage. Based on this information, lathering with apple cider vinegar alone seems to pass but baking soda does not.
But how about diluting baking soda?
It turns out that baking soda actually retains its high pH even when diluted. In fact, the bicarbonate ion found in baking soda has a “buffering capacity and the ability to neutralize both acids and bases.” That’s why it works so well in your refrigerator to get rid of unpleasant smells.
But back to one of our original questions — why do some people react better or worse to this concoction?
Well first off, those with chemically treated hair will mostly have a different reaction, as bleached hair has a low pH. Because the hair’s pH is lower, the baking soda mix can cause more damage than someone whose hair has a higher pH. Second – all hair products have different pH levels. In her original post, Jennifer used a Giovanni tea tree oil shampoo, which worked for her greasy scalp.
If you’re looking to replicate Jennifer’s mixture for treating your greasy scalp, here are 2 ideas you can try after first rinsing with apple cider vinegar as she recommends in Waxy, Greasy Hair After Shower: A Surprising Form of Dermatitis.
1) If you are currently diluting your baking soda in water, you may want to replicate’s Jennifer’s method, which is to dilute baking soda in shampoo. Shampoos usually have a lower pH than water. Again you can use the same tea tree oil shampoo Jennifer suggests.
2) If you are currently diluting baking soda in shampoo and having problems, consider using a different shampoo. All shampoos have different pH levels. Perhaps, a shampoo that is lower pH or higher pH may work for your greasy scalp.
What works for your waxy buildup on scalp? Share it with us!
Bio: Allan helped his dad with eczema to research natural remedies to heal his skin and break the itch scratch cycle without relying on steroids. To read the story of how he gained control of his eczema after 10 years of itching and scratching, please Eczema Detective. You’ll learn about three things that were key for him to go from sleepless, scratchy nights to (mostly) flare-free.
Disclaimer: I am not a doctor or medical professional at all, so please do not consider this medical advice.
 The Shampoo pH can Affect the Hair: Myth or Reality? https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4158629/
 Robbin, Clarene R. Chemical and Physical Behavior of Human Hair. Fourth Edition. 2002. Pages 402.
 Effect of apple cider vinegar on delayed gastric emptying in patients with type 1 diabetes mellitus: a pilot study https://bmcgastroenterol.biomedcentral.com/articles/10.1186/1471-230X-7-46
 Baking Soda Destroyed My Hair https://blog.kanelstrand.com/2014/01/baking-soda-destroyed-my-hair.html
 Robbin, Clarene R. Chemical and Physical Behavior of Human Hair. Fourth Edition. 2002. Pages 250.
 Skin Surface pH: A Protective Acid Mantle https://www.sebamed.fr/client/document/2-skin-surface-ph_94.pdf