Soap and pH - Recovery time

Yesterday we learned that between the pH range of 4-9, hair really does not show any surface or internal changes. Now we focus on the surface and chemical changes that may occur.



Note: Hair is known to have a slightly acidic pH but there is great variance among individuals. Scientific studies have reported values as low as 3 and others as high as 6.6.



Q1: After using soap, does the pH of hair change?



The most likely answer is yes. I could not find an answer directly about hair but I did find one on skin. Even washing with water produces a change in pH, however soap does produce the most change (Dermatology pp258-262, 1997)

Wash Product	Product pH	pH change to skin
Tap water	7.9	+0.198
Synthetic detergent 1	5.5	+0.294
Synthetic detergent 2	5.5	+0.291
Soap	9.5	+0.453

Anywhere from 45 minutes to 3 hours (British Journal of Dermatology, Volume
76, Issue 3, pp 122-125, 1949)





Yes washing regularly and repeatedly with soap is thought to disrupt the normal flora of the skin. (In case you didn't know, we are crawling with bacteria and this is normal). Disruption of this bacteria can lead some to proliferate more than others (Acta Derm Venereol.;67(1):41-7, 1987). Please do note that this has to be regular and repeated (for example twice a day, every day).






Let me start by saying the normal test to look for sensitive skin is to use SLS, a superb surfactant. Regardless of pH, it can be very irritating. Do remember irritance comes from removal of the oil layer causing dryness and itchiness. 



There is a strong relationship between pH and irritancy. Generally between ph 4 and 9, there isn't much irritation (meaning it may still be there but will not be disturbing). Outside this range, irritation can increase markedly (International Journal of Dermatology, pp494–499, 2002)



Depending on the pH of your baking soda mix or castile soap dilution, you may experience irritation.





I will save the juicy questions for last - Tune in tommorow for Q&A: Should you really use castile soap and or baking soda ( including silicone removal and whether pH is sufficient to relax hair).