Home Cosmetic Science Talk Formulating Low pH vs neutral pH shampoo mildness comparison

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  • vitalys

    Member
    October 7, 2021 at 2:21 pm

    I wonder what do authors of the study as well as the marketing leaflet consider to be “milder”? 

  • abdullah

    Member
    October 7, 2021 at 3:17 pm

    @vitalys the comparison in this photo is zein test.
    The comparison in link says dryness comparison. 

  • vitalys

    Member
    October 7, 2021 at 5:06 pm

    @Abdullah I doubt the formulations at pH7 could be milder in terms of “dryness” especially in long term perspective. The neutral and alkaline pH ( for the SC) inhibits important enzymes, including those that regulates lamellar bodies, which produce intercellular lipids. At the same time pH 7 and higher hydrates (not moisturizes) the Stratum Corneum for a short period of time. After that water evaporates quickly. Hyperhydration leads to disruption in corneocytes packing. I guess, authors considered short period of time of hyperhydration to be “milder”. Only buffering system of the skin helps to recover the normal (acidic) pH after use. 

  • vitalys

    Member
    October 7, 2021 at 5:09 pm

    This old diagram explains the correlation between pH and electric charge. 

  • zetein

    Member
    October 8, 2021 at 12:24 am
    @vitalys In practical terms I am going to rinse with tap water which is pH 7-8 anyway. So the pH only affect the washing/lathering process, afterwards, hardly. The rinsing would bring up the pH of post-wash skin to ~7 regardlessly.
  • zetein

    Member
    October 8, 2021 at 12:54 am
    The zein test is a very sketchey ex-vivo test that uses dead vegetable proteins and the duration can be hours. It doesn’t really apply to how surfactants was used in practice. Also the results can be conflicting sometimes. IMO shouldn’t be taken too seriously on its own.
    This article should interest you:
    Also take note of this sentence below
    From our previous work (8), we know that in the presence of the ammonium ion, the zein test underestimates the irritation.

  • abdullah

    Member
    October 8, 2021 at 2:13 am

    @zetein thanks for the file.
    Does this text mean ammonium ion makes it milder in zein test?

    And do you know where can we find this previous work of theirs?

  • abdullah

    Member
    October 8, 2021 at 2:17 am

    vitalys said:

    This old diagram explains the correlation between pH and electric charge. 

    @vitalys does this chart mean below 4 skin has positive charge and above 4 negative charge?

    Also where did you get this char? 

  • abdullah

    Member
    October 8, 2021 at 2:20 am

    vitalys said:

    @Abdullah I doubt the formulations at pH7 could be milder in terms of “dryness” especially in long term perspective. The neutral and alkaline pH ( for the SC) inhibits important enzymes, including those that regulates lamellar bodies, which produce intercellular lipids. At the same time pH 7 and higher hydrates (not moisturizes) the Stratum Corneum for a short period of time. After that water evaporates quickly. Hyperhydration leads to disruption in corneocytes packing. I guess, authors considered short period of time of hyperhydration to be “milder”. Only buffering system of the skin helps to recover the normal (acidic) pH after use. 

    When i tested I also felt the same product at pH 5 was milder than 7 but that maybe just my imagination because i wanted to be like this. 😀

  • DaveStone

    Member
    October 8, 2021 at 3:41 am

    zetein said:

    @vitalys In practical terms I am going to rinse with tap water which is pH 7-8 anyway. So the pH only affect the washing/lathering process, afterwards, hardly. The rinsing would bring up the pH of post-wash skin to ~7 regardlessly.

    But if that’s the case, then you might as well wash your face with Irish Spring or baking soda…
    I think the PH of the soap still has an effect on your face, regardless of the water.
  • zetein

    Member
    October 8, 2021 at 5:09 am
    @DaveStone Post was talking about acidic or neutral-as-water cleansers based on synthenic surfactants. Alkaline fatty acid soaps should never be recommened as it directly neutralize intercellular lipids and also leave scums onto skin and cause irritation.
    pH7 products won’t do this. And their effect on the pH balance of skin is negligible because it’s the same as that of tap water in the rinsing process which is an inevitable despite the acidic cleanser you might use.
  • abdullah

    Member
    October 8, 2021 at 6:07 am

    zetein said:

    @DaveStone Post was talking about acidic or neutral-as-water cleansers based on synthenic surfactants. Alkaline fatty acid soaps should never be recommened as it directly neutralize intercellular lipids and also leave scums onto skin and cause irritation.
    pH7 products won’t do this. And their effect on the pH balance of skin is negligible because it’s the same as that of tap water in the rinsing process which is an inevitable despite the acidic cleanser you might use.

    I think water vs surfactant at ph7 is not the same because water is weakly and surfactant is strongly buffered. At least stronger than water.

    Same as a glass of lemon juice vs a glas of water with a teaspoon of lemon juice. Both will have pH 2 but the effort from pH 2 in pure lemon juice is stronger. 

  • ariepfadli

    Member
    October 8, 2021 at 9:05 am

    sufactant means surface active agent need to reduce surface tension of solvent
    for ability for cleaning its depend on HLB proportion, low HLB will much likely love oil and emulsify it into solvent (in this case are water), and strip your natural skin oil

    more non polar tail on surfactan will act more agresive it solubilize your oil
    more easily Polar head ionize show how many of surfactant will active in sytem (and this depend on pH and you polar head anionic, cationic, amphoteric or non ionic on your surfactant)

    base in this you can choose what surfactant that harsh/ iritant or “more safe based on your formulation pH

    example: if i coose Sodium (head) lauryl( tail) sulphate (anionic) it will more alot surfactan active  at base (>7)pH since on whole head already in soluble form, and you make it more mild in slightly acid pH because at acidic state surfactan anionic not all in active form

  • vitalys

    Member
    October 8, 2021 at 11:30 am

    @ariepfadli Perfect explanation! 

  • vitalys

    Member
    October 8, 2021 at 11:34 am

    @Abdullah it’s from “Chemistry of human epidermis” by Wilkerson

  • vitalys

    Member
    October 8, 2021 at 11:53 am

    @zetein Yes, but they compared “mildness”. I don’t think pH7 is something awfully dramatic for the skin unless the skin is healthy. Anyway, the buffering system recovers physiological pH quickly. However, the continuous use of surfactants with higher pH can affect skin. 

  • abdullah

    Member
    October 11, 2021 at 3:27 am

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