15 Most Common Harmful Ingredients in Your Shampoo - Banner

15 Most Common Harmful Ingredients in Your Shampoo

A complete list of 15 of the most common harmful shampoo ingredients that you should pay attention to and why.


In today’s society, people are becoming more conscious about living a healthier lifestyle. From food, daily consumer products and to exercising regularly. But how familiar are you with the ingredients that go into your shampoo? I am guessing the answer is probably not very.

Even with the best intentions to read the labels at the back of the bottle, most of us will give up trying to understand all the scientific terms by the second line. We then allow other factors like, scent, colour, brand and reviews to guide us in making our purchase decision.  

Listed below is a complete list of 15 of the most common harmful shampoo ingredients that you should pay attention to – and why.

1. Ammonium Lauryl Sulfate or Sodium Laureth Sulfate (SLES)

Sulfates are a very common ingredient in shampoos. When you rinse out the shampoo, the surfactants take all the sebum with them. These cleaning agents are so harsh, they can damage the hair, make it brittle and increase frizz. They can also cause allergic reactions in people with sensitive skin.

2. Sodium Lauryl Sulfate (SLS)

This detergent works the same way as the two mentioned above. In addition, it creates the lathering foam. Most of us feel we do not get sufficiently clean hair without the foam, though that is not the case. SLS can have mutagenic properties and other toxic effects on the human body.

3. Parabens

Parabens are used as a preservative to prevent bacteria from growing in cosmetics and shampoos, and it is likely that our skin can absorb them during topical use. Parabens can mimic the hormone estrogen and have been linked to an increased growth of breast cancer cells.

4. Sodium Chloride

Sodium chloride is simply salt. It plays the role of maintaining thicker consistency in shampoos and conditioners. Salt can make an already sensitive scalp dry and itchy, which can eventually be a cause of hair loss.

5. Polyethylene Glycols (PEG)

PEGs are also thickening agents that are often contaminated with byproducts like ethylene oxides and 1,4-dioxane that are harmful.

6+7. Diethanolamine (DEA) and Triethanolamine (TEA)

DEA and TEA are emulsifiers and foam agents that reduce the surface tension between different substances so that ingredients that are water-soluble and oil-soluble can blend together. In 1998, researchers found a link between the topical application of DEA and cancer in animals during lab tests. According to the Food and Drug Administration, however, there are no proven links between the use of DEA and cancer in humans.

8. Formaldehyde

Out of all the shampoo ingredients that are harmful, formaldehyde may be the scariest. Formaldehyde is a known human carcinogen and has been proven to be absorbed through the skin in animal testing. The formaldehyde-releasers have different names and it will not always be clear what they actually are but the common one in shampoos is quaternium-15.

9. Alcohol

Alcohol is a very common component in shampoos. Most alcohols have a drying effect, and the higher up in the ingredient list it appears, the more of it the product contains. Some alcohols that are not as bad for dry hair start with a “C” or an “S”, like Cetearyl alcohol and Stearyl alcohol. They can actually help your hair retain moisture. The ones that are bad if you already have dry hair usually have a “prop” in their name, like Isopropyl alcohol or propanol.

10. Synthetic Fragrances

Products that have “fragrance” on their label contain thousands of hidden chemicals. Some ingredients in fragranced cosmetic products can disrupt the reproductive systems. They can also cause cancer, asthma and make their way into women’s breast milk. Like many ingredients on this list, it is also an irritant to the skin and scalp, which can lead to hair loss.

11. Synthetic Colors

Most shampoos and conditioners are dyed with a synthetic color to make them look nice. These colors come from petroleum or coal-tar sources, all of which come with harmful health effects. Many have links to various diseases – even cancer, and are already illegal abroad. Synthetic colors will normally go by FD&C or D&C combined with a number.

12. Dimethicone

A type of silicone, dimethicone is basically plastic that contributes to product buildup making your hair feel greasy to give the illusion that your hair look shiny. In reality, it weighs the hair down, making it heavy, limp and lifeless. Hair and scalp that are “coated” with this plastic film stop moisture and nutrients from coming in and can clog pores on your scalp causing skin irritation or hair loss.

13. Cocamidopropyl Betaine

Even some shampoos claiming to be natural and organic, contain cocamidopropyl betaine, which is another foam booster. Do not let the fact that it is a natural compound from coconuts trick you! Hair products use it together with something called dimethylaminopropylamine which can cause skin irritation, allergy, rosacea, and eczema.

14. Triclosan

Triclosan was banned from being used in antibacterial soaps in 2016, but ironically it is still an allowed ingredient in other household staples, such as toothpaste, shampoos and deodorants. This is a chemical antibacterial agent that is known to cause hormone disruptions, which can cause cancer, neuro developmental problems and affect fetal developments.

15. Retinyl Palmitate

Some shampoos contain retinyl palmitate, which when in contact with skin, converts into retinol. This is a known skin irritant and can cause peeling, scaling, redness, and itching. There are warnings about side effects from retinyl palmitate including cancer, reproductive problems, and organ toxicity.

The sad reality is that it is impossible to avoid all of the above ingredients completely in shampoos but it’s good to have some knowledge in order to make better informed decisions.

Katherine Tan

13 Mar 2019, 03:41 PM

With almost 20 years of experience behind the chair, Katherine is a hidden gem with a loyal clientele from the media industry. Her passion for hairstyling & communication made her the first hairstylist/writer in Singapore. Katherine’s mission is to share her expertise and best finds from the hair industry through the lense of a hairstylist. She is also the Founder of Salon Now - a platform dedicated to engage, educate and elevate hairstylists in Singapore and all around the globe.