Composition of acid mantle and how is it made

AbdullahAbdullah Member
According to google, when sebum is mixed with sweat, it makes the acid mantle.

As i don't trust google ;) i want to learn the answer to these questions from you chemists.

Questions:
1. What is the composition acid mantle and how is it made?

2. If it is mixture of sebum and sweat, then if we wash our skin daily or twice a day with surfactant, does it means we have no acid mantle because we remove all the sebum and sweat?

3. Even if we wash our skin with water alone that removes sweat but not sebum, does it mean we don't have acid mantle because sebum alone doesn't make acid mantle?

4. Those parts of our skin that doesn't produce sebum, do they ahave acid mantle? If yes then how?
 
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Comments

  • chemicalmattchemicalmatt Member, Professional Chemist
    @vitalys thanks for all these links. You are a generous soul and tribute to the science of personal care.

  • @vitalys thanks for all these links. You are a generous soul and tribute to the science of personal care.

    You hit the nail on the head.  Vitaly is an asset to this community, and the world.
  • AbdullahAbdullah Member
    @vitalys thanks a lot. 

    I wasn't available for some days. 
  • vitalysvitalys Member
    @chemicalmatt @Graillotion Thank you for the kind words, dear colleagues. It is just a small part of the skin knowledge, which is always useful in cosmetic formulating work. 
  • vitalysvitalys Member
    @Abdullah you are very welcome


  • AbdullahAbdullah Member
    A chemist here once told me that skin and hair doesn't have pH. The have isoelectric point.
    Skin isoelectric point is ~4.8 
    Hair isoelectric point is ~3.6

    These papers all say skin pH is this and that. 

    Maybe i haven't understood it correctly so i am asking it once again. 

    does skin have pH?
  • SquinnySquinny Member
    vitalys said:
    @Abdullah
    The questions you ask deserve the whole article or books. 
    You will find all the answers here: 


    Wow great articles thanks for sharing - really appreciate it.
  • vitalysvitalys Member
    @Abdullah
    Certainly, it has pH, because isoelectric point (IEP or pl) is pH. 
  • PerryPerry Administrator, Professional Chemist
    @vitalys - Perhaps it is semantics but pH is a measure of the amount of [H+] ions in a water solution. For something to have a pH it has to be liquid by definition. Skin is not a water solution, thus it does not have a pH any more than a chair, a table, or a refrigerator has a pH.  Am I missing something?

  • vitalysvitalys Member
    @Perry Epidermis and especially dermis contain water, i.e., water solution of electrolytes, etc. It means that pH is measurable. I must say even more - pH is a key factor to make multiple enzymes work, which is important for instance for such physiological processes as proper keratinization or lipid formation in keratinocytes. Skin even contains the special proteins for the water transportation - aquaporins. 
  • AbdullahAbdullah Member
    @vitalys what about Stratum Corneum? Does it have water? Because this is the outermost layer and what will be in contact with cosmetic products.
  • vitalysvitalys Member
    @Abdullah Yes SC is hydrated, which means it contains water to some limited extend. SC is highly dynamic structure. The hydration of SC defines the local homeostasis of SC, the proper structures of the lipid bilayers and the degree of this hydration depends on the blood microcirculation in the upped dermis and the outer humidity and environment. 
    The SC water content and water retaining capacity of corneocytes and NMF depends on different skin conditions or skin pathologies too. See the picture attached. 

  • AbdullahAbdullah Member
    @vitalys thanks 
    Is this photo from a book? 
  • vitalysvitalys Member
    @Abdullah Sorry I didn't mention the source.
    Masanori Takenouchi, M.S., Hiroyuki Suzuki, and Hachiro Tagami, M.D. "Hydration Characteristics of Pathologic Stratum Corneum-Evaluation of Bound Water" Department of Dermatology, Tohoku University (HT), Sendai, Japan
  • PhilGeisPhilGeis Member, Professional formulator
    Here's the link - https://www.jidonline.org/article/0022-202X(86)90008-4/pdf
    I'd not get carried - no standard deviation in this or Fig 1.
  • AbdullahAbdullah Member
    PhilGeis said:
    Here's the link - https://www.jidonline.org/article/0022-202X(86)90008-4/pdf
    I'd not get carried - no standard deviation in this or Fig 1.
    It says This page does not exist.
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