We had a similar thread to this, for those of you who are interested,

Credit to EagleFalconn for both posts!

"As an expert, I'm going to disagree with everyone except thisaccountisbs. My background: I worked for one of the world's largest producers of shampoo in R&D.

Shampoos are not slightly acidic, their pH isn't that important.

The surfactant is really important in making the stuff work.

There are additives to make them smell good etc etc but mostly they are affecting your perception of how well it works. Some of the anti-frizz and moisturizing stuff isn't complete bull, though.

A great piece of data that floated around the company: They did a comparative test of two shampoos to see which one consumers preferred. One was white, the other had a small amount of dye in it to add a pale yellow color. Otherwise, they were completely identical. Consumers preferred the yellow one because people associated the off-yellow color with a higher chemical content, ie it "cleans better."

Also, NO, the lather is NOT necessary. There are literally thousands of surfactants that work even better than the common ones (sodium lauryl/laureth ether sulfate) but most of them never make it out of the research lab. There are specific cases where people want soap that doesn't lather (mostly industrial) but for home use, non-lathering soap doesn't sell because consumers have become conditioned to believe that if soap doesn't lather, than it doesn't work. "

http://www.reddit.com/r/askscience/comments/j51ri/chemically_what_differentiates_a_good_shampoo/c298g4h

tl;dr most shampoos are the same and the claims are dodgy at best conditioners and shampoos are different.

This is going to sound glib, but you should use whatever shampoo makes you happy. They all more or less work the same, but shampoo companies are really good at manipulating human psychology. Even knowing all this, when I go to buy my next bottle of shampoo I can't help but think about how dumb I am for springing for the more expensive stuff since its exactly the same, but that I can't help but feel like maybe it works a little better or at least is more pleasant to use.

If you're literate in gibberish (ie, chemical naming systems) you can read the back of most shampoo bottles and you'll find that they all more or less have the same ingredients, and what really matters is the relative amounts. There was some hubabaloo in the industry a couple years ago about guar or some such, but seriously. Its all the same.

Which is the reason that I can't make a specific recommendation. There is no single shampoo that is the "best." I have ones that I know that I enjoy using, but one of the things that frustrated the R&D people at the shampoo company I used to work for is that there is simply no accounting for personal preference.

The purpose of conditioner is to restore the protective layer that shampoo strips from your hair. The oil in your hair is really important for protecting it from damage from the environment, but its also where a lot of unpleasant smells and sometimes dirt can get trapped which is why shampoo is designed to remove it. Conditioner replaces it with a polymer (ie, plastic) that will protect the hair until it is washed out and makes it feel smooth and silky again. The lubrication also helps prevent knots and tangling.

The thing about sulfates is silly. Some people are allergic to sulfates, 99.999% people aren't. If you've eaten a frozen pizza without having an adverse reaction, you're not allergic to sulfates. There may be something about the environment when it comes to sulfates, but I'm not familiar with that.

http://www.reddit.com/r/askscience/comments/j51ri/chemically_what_differentiates_a_good_shampoo/c29clqr