Generalities on tensioactives
♪ tensioactive compounds are ampphilic molecules, that is, they present two parts of different polarity, one lipophile (which retains fat) and apolar, the other hydrophilic (miscible in water) and polar.
In contact with the water, the agents of the tensioactive foam, wind and emulsion, activate to detach the fat deposited on the surface of the hair.
The more they foam, the more dirts disperse and the greater the action.
Tensioactives are therefore washing agents or detergents depending on the product used.
The 4 major types of tensioactive
- Anionic tensioactive: the hydrophilic part is negatively charged.
- Cationic surfactants: the hydrophilic part is positively charged.
- The zwitterionic or amphoter surfactants: the hydrophilic part has a positive load and a negative load, the overall load is zero.
- Non-ionic tensioactive: the molecule has no net load.
This can be for example ammonium lauryl sulfate, ammonium laureth sulfate, sodium laureth sulfate (irritant, sensitizing and drying) or sodium lauryl sulfate (most aggressive). Ammonium lauryl sulfate is one of the least aggressive washbasins (not to be confused with ammonium laureth sulfate).
Ammonium lauryl sulfate
In this oil there are mainly 3 fatty acids, which are lauric acid (C12H24O2 ), myristic acid (C14H28O2) and palm acid (C16H30O2).
The chemical composition of coconut oil is remarkable by its high rate of short-chain fatty acids and low unsaturation rates. This naturally gives it a high saponification index.
In this mixture of fatty acids, sulphur neutralized by ammonium is incorporated to create a product made of lauryl ammonium (C12H29NO4S ) , myristic (C14H33NO4S) , palmitic (C16H37NO4S) sulfate.
Ammonium Lauryl Sulfate (ALS) Although classified as irritant (Xi) in pure condition, does not present a known risk to the user as it is not intended to be left on the skin (shower gels or shampoos that contain them are normally rinsed).
In a report published in 1983 on the follow-up of cosmetic ingredients, 6 out of 6,8 million shampoings were raised, with a maximum concentration of 31% of ALS: 2 itchings of the scalp, 2 allergic reactions, 1 abime hair, 1 eye irritation).
This report concluded that Cosmetics containing SLA should be used periodically, in short use and followed by rinsing. Otherwise, the concentration of SLAs should not exceed 1%.
A study conducted by The Human and Environmental Risk Assessment (HERA) on alkyl sulphates, also applicable to SLAs, found possible irritation of the skin and eyes. This irritation depends on the SLA concentration.
After a two-year study on rats, HERA found that Ammonium Lauryl Sulfate is not carcinogenic in skin application.