INCI – How to read it? Harmful substances in hair care products

by Catelyn Cox

Nobody likes irritations, dehydrated hair or allergic reactions. While buying a shampoo or a conditioner we want to trust the product completely without worrying whether it would harm us or not. However, the beauty product lists of ingredients leave a lot to be desired and frequently hide substances that instead of taking care of hair – damage it. What and how should we avoid them? What should we pay attention to while buying a hair care product?

INCI: Harmful substances in hair care products


These are preservatives. In short, they extend the shelf-life of either a shampoo or conditioner. Parabens are liked by cosmetic manufacturers because they don’t affect the way a particular product work (don’t weaken the product’s performance), but just preserve it. The popularity of parabens is owed to their ability to slow down the multiplication of microorganisms that gather on skin and protect a cosmetics from bacteria. And this is how they extend shelf-life of many cosmetics.

On the flip side, when used in galore, they happen to be harmful. They are said to display cancerogenic action and might cause hormonal disorders. Shampoos frequently house the following parabens: phenoxyethanol, methylparaben, ethylparaben, propylparaben, butylparaben, isobutylparaben. Naturally, each of them has a different ‘damaging tresold’ and when in a low concentration they aren’t harmful to an organism. However, it’s worth realising that in most cases we use more than just one product containing parabens. For that reason, the doses of parabens are getting bigger with every another product applied, and the toxic action is getting more potent.


This is a group of substances that is frequently added to shampoo and conditioner compositions. Silicones are present in lotions, leave-in conditioners, heat protection sprays and are a common constituents of oily hair conditioning serums. Hair masks feature silicones, too.

Frequently, they are simply called ‘silicone oils’ because they are oily and sticky. Sadly, they have nothing in common with natural oils. Silicones come into existence by combining silicon with oxygen. They improve product’s consistency and influence the way the cosmetics are spread on skin and hair. The truth is, silicones are widely used and (paradoxically) welcomed in hair care products because putting them on hair boosts hair condition immediately. To clarify, hair turns into being smooth, shiny, tamed and simply more beautiful.

Sadly, heavy silicones work comedogenic and residue on skin and hair to such an extend that only a strong shampoo with potent cleansing agents is able to remove them.

Hair care products should contain only volatile silicones because right after application most of them is released so they don’t residue on either hair or scalp. Heavy silicones are: simethicone, trimethicone, trimethylsiloxysilicate, trimethylsilylamodimethic, to name just a few.


SLS, sodium lauryl sulfate, is an aggressively working detergent used in almost all washing beauty products, not only in hair care products.

SLES, sodium laureth sulfate, is produced from ethylene oxide which action can be compared to SLS. It’s a crude oil derivative and displays lathering properties therefore it’s added to shampoos and other similar washing products (including domestic detergents).

Both SLS and SLES are synthetic detergents that have adverse, irritative influence onto skin. They can cause itchiness, acne, eczema and dehydrate skin.


They are crude oil derivatives. One of mineral oils representatives is paraffinum. The beauty industry use them eagerly mainly because of their lubricating properties. In short, they work like emollients and almost in no time they are able to improve the look of skin and hair. They prevent epidermis and hair against water loss. Another asset of mineral oils is their astonishingly low cost, which is one of the reasons why they are so commonly used in beauty supplies production.

Unfortunately, mineral oils aren’t well-tolerated by our skin and hair. They work comedogenic and clog cells. Moreover, they are able to build up on skin and hair roots creating an impervious occlusive layer. It can be compared to putting on an invisible foil that suffocates skin and hair. In other words, it impedes gas exchange.


Aluminum – probably almost everyone is well-aware of the harmful effect it has on the human body. A lot has been said about the adverse action that antiperspirants display, which was often mentioned while discussing the subject of cancer prophylaxis. Aluminum is one of the most commonly used substance added to various cosmetics which aim is to regulate sebum production. It can be also found in hairsprays and some dry shampoos. In short, it clogs skin pores and blocks sebum secretion. This chemical element is infamous for residing in tissues, irritating immune system and even being able to damage other systems.

6. PEG

This is an abbreviated name of polyethylene glycol. When added to beauty products, it plays the role of emulsifier, solvent and other agents that are to make a product denser. Glycols are responsible for the consistency a particular product has. Sadly, they can’t be produced without making use of harmful ethylene oxide and cancerogenic di-oxidants.

Glycols are reported harmful, especially if used in high concentrations and huge amounts. They are able to keep accumulating in body tissues and organs for years. Naturally, the less a cosmetic has them, the better. Luckily, they can be easily recognized by looking at INCI. They go with PEG/PPG prefixes (e.g. PEG-40 sorbitan diisostearate, PPG-15 stearate) or, which is even more frequent, suffix -eth (e.g. laureth-8-phosphate).


A huge and frequently used group of substances. Basically, there are a few various alcohol types. Luckily, the great majority of them deliver beneficial action to hair and scalp since they moisturise and condition hair, being at the same time an important factor that bonds emulsion. Moreover, they facilitate penetration of active substances through skin and hair layers. The very beneficial alcohols are the ones belonging to di- or polyhydric and long-chain fatty acid group. They form a protective film on the surface of the hair and leave strands soft. The most popular ‘good’ alcohol is glycerin.

The flip side is of course the ‘bad’ alcohol group that displays dehydrating action. They damage hair and cause allergies in scalp. Frequently, they are added to hair care products (but not only) due to their low cost. This group of alcohols is called monohydric and displays negative action in hair by weakening the entire length of strands, depriving them from shine and elasticity. For that reasonm, it’s worth knowing the names of the biggest hair enemies to avoid them. They are: alcohol denat (also known as SD alcohol), benzyl alcohol, ethanol alcohol, grain alcohol, isopropanol alcohol, isopropyl alcohol (IPA), propanol alcohol.

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