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topic 6695

Why is citric acid in shampoo and conditioner?


Q. I am doing research in my Chem 2 class on why certain chemicals are in household products and I was wondering if you could tell me why Citric Acid is in many shampoos and conditioners. If you could tell me it would be great. Thanks

Kasey S [last name deleted for privacy by Editor]
- Chesaning, Michigan


A. Citric Acid isn't used because of the smell. Fragrances are added for that purpose. It has a two-fold reason for addition. Shampoos usually are at pH 5.5 because at slightly acidic pH the scales on a hair follicle lay flat making the hair feel smooth and look shiny. Citric acid is used to adjust the pH down to 5.5 (ish). It is a fairly weak acid which makes the adjustment easier. it also has a small amount of preservative action. Citric acid as opposed to any other acid will prevent bacterial growth. (I used to work in the lab for a cosmetics company)

Ciaron Murphy
Nordam Europe - Great Britain

Making Natural Liquid Soaps: Herbal Shower Gels, Conditioning Shampoos ...
from Abe Books


thumbs up sign"I used to work in the lab for a cosmetics company"

It shows, Ciaron. Thanks for the great answer!

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


!! Hey thanks for the great answer! It really helped me on my science fair project!

Rebecca [last name deleted for privacy by Editor]
- NLR, California


Q. Wow...Thanks for the info, but what is pH 5.5?

Pat [last name deleted for privacy by Editor]
- Gaithersburg, Maryland



A. The full definition of pH is: "the negative antilog^log of the hydronium ion concentration", but I don't know if that information is beyond your grade level, Pat. The easier way to look at it is that a pH of 0 is as acidic as you can get, a pH of 14 is as alkaline as you can get, and a pH of 7 is neutral.

Again, depending on what grade you're in, you may or may not have been taught logarithmic scales. In a logarithmic scale you "count the zeroes". So a pH of 5.5 is slightly acidic, but it's less acidic than a pH of 5.0. And in turn, a pH of 5.0 is only one-tenth as acidic as a pH of 4.0, only one-hundredth as acidic as 3.0, only a thousandth as acidic as 2.0, etc. Good luck!

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

July 18, 2012

@ Ted Mooney, P.E. RET
First of all...
"The full definition of pH is: 'the negative antilog of the hydronium ion concentration' ".

WRONG!!! Clearly this is a bit "beyond your grade level" but pH=-log[H+](base 10 of course), just negative log, not antilog.

"The easiest way to look at it is that a pH of 0 is as acidic as you can get, a pH of 14 is as alkaline as you can get"

ALSO WRONG, I'm guess you don't even know what a logarithm is based on that explanation, extremely acidic solutions can have a negative pH, and similarly extremely alkaline solutions can have pH's above 14, some hair care products used in salons get as high as pH=17.

I appreciate the sentiment trying to help this kid out but check your facts.

T.J. Campbell
Cal State Univ. Chico - Chico, California, USA

July 18, 2012

Thanks T.J.

You're right that pH is the negative log, not the negative antilog; thanks for correcting a silly mind-slip.

Not knowing what grade Pat is in, my "easiest way of looking at it" seemed sufficient; it's the way dozens of different textbooks have described it for decades, and it's defended by numerous "ask a scientist" pages -- but, yes, nearly every explanation is a simplification. Were I to say that processes range from 0 to 100% efficient, you could point out processes of over 100% efficiency too.

Pat might be a 3rd grader or s/he might be a senior in high school; since I don't know, starting with "depending on your grade level" seemed the proper preface to avoid patronizing him/her. But your use of "beyond your grade level" was deliberately snide and insulting. And you are honestly guess that a professional engineer doesn't "even know what a logarithm is", do you?

For 23 years now we've worked hard to make this site "... a place of camaraderie ...", and to maintain "... a friendly, welcoming atmosphere ..." (something that grows in importance in our increasingly polarized society). So I'd appreciate you saving ALL CAP, multiple exclamation point, snide comments for your Youtube and Facebook postings. Pat and I are not the only ones in this 3-way conversation who still have something to learn.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey


Q. Hiya. I'm 10 years old, and 27 of us kids (and 1 teacher) want to know whether shampoo is an acid, base or neutral. I'm in Grade 6.

Christopher J.
I'm just in Grade 6! - Bundaberg, Qld, Australia


A. Ciaron Murphy already answered this question on this page, Christopher. If it wasn't clear enough, can you please rephrase your question in terms of the answer that he already gave, so that we can feel comfortable that you are trying to use this site to learn, rather than to ask someone to post an answer that you can cut & paste for your homework ? Thanks!

Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

March 18, 2008

Q. Thanks for the help everyone; it really helped me on my E.C. health homework. I was just wondering if citric acid is in bath and body volumizing shampoo?

Tom B [last name deleted for privacy by Editor]
homework - St. Paul, Minnesota

Why is shampoo acidic and conditioner alkaline?

June 19, 2008

Q. Most shampoos that we use everyday are acidic while conditioners are alkaline. Why are these shampoos and conditioners manufactured to be acidic and alkaline respectively? What are the benefits to hair care? Can you please also enlighten me on how 2-in-1 shampoos work? Thank you!

Wei L [last name deleted for privacy by Editor]
student - Singapore

What is right pH for shampoo?

October 6, 2008

Q. What pH should shampoo & conditioner have?

Sarah W.
student - England

A. Hi, Sarah. Half of that answer is on this page already. Please try your best to phrase your question in terms of what has already been said so that we can keep moving forward. Thank you.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

Forever New Fabric Wash

February 19, 2010

Q. Hi, I am Trina, Manager, of a Boutique in Williams Lake, B.C

We sell a mild detergent called 'Forever New', (citric base). It prevents the elasticity in under garments from breaking down. I have had no complaints with this product, though I have had one customer enquire about it, because she has had a reaction to one of two products she is using in her home. I have been helping her with new information, and am trying to get a little bit more :) Any suggestions would be very beneficial for myself and my customers.

Thank-you Very Much
Kind Regards

Trina Casler
supervisor sales associate - Williams Lake, B.C., Canada

February , 2010

A. Hi, Trina.. Citric-based means based on citric acid, which is an acid in citrus fruits. But chemical formulations are complex. You should probably ask the manufacturer for the MSDS for this product (material safety data sheet) and pass that on to your customer. Good luck.


Ted Mooney,
Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

September 22, 2012

Q. Hello,
I'm venturing into the world of homemade hair care and I'm trying to make a coconut oil based conditioner (along with neem oil, tea tree, rosemary & lavender essential oils) that rinses out well and doesn't leave hair oily. We have very fine hair and oily scalps so this is definitely an issue. Would adding citric acid to my recipe help with this? I know there are many other oils I could use, but the coconut oil is particularly important because it helps deter lice (something that's a big problem in this area and I want to be preventative). Thanks so much!

Lara Strickler
- Bainbridge, Pennsylvania, USA

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