Ingredients Dictionary: Your help needed!

I have a new series idea, Monday will be the ingredients dictionary day. Each week I will feature an ingredient (or set of ingredients) and highlight how it works and if it works well in combination with other ingredients. I will also highlight the good and bad points of each in a simple format (for example a rank out of 5)

The proposed format will look a little bit like this

Ingredient: Sodium Lauryl Sulphate

Use: Cleansing in Shampoo (removes oil layer)
Advantages: Near complete removal of oil (clarifying)
Disadvantages: Irritating (removes oil layer and can cause dryness and itching for upto 10 days)
Common myths: Causes Cancer and Hair loss
Best practice use: As a clarifying shampoo to remove build up
Best practice combinations: Combine with less irritating surfactants such as SLES or Cocobetaine. Addition of silicones in shampoo formulae for conditioning

Positive properties rating (Scale of 1 to 5 where 1 is mildly effective and 5 is highly effective)
Cleansing: Very effective oil removal  - 5/5
Moisturising: Not a moisturiser           - 0/5
Conditioning: Not a conditioner          - 0/5

Negative properties rating (Scale of 1 to 5 where 1 is mild reaction and 5 is severe reaction)
Irritancy: Highly irritating (on its own)  - 5/5

Further reading and Sources
(I would place any relevant posts with journal citations or journal citations)

The idea is to have a list eventually which you can simply print off (like a selection of cards) and keep to use if you need to know what an ingredient does and how it works.

So it is over to you now, name the ingredients that you would like to see featured! Plus if you have heard or read something specific about any ingredient, please mention it! If you would like the list to feature additional properties then also mention this!