6 common questions about hair thickening fibres

Understand the different types of hair thickening fibres and their effects

There are a lot of myths out there about hair thickening fibres and we get a lot of the questions from our readers so we thought it might be a good idea to dispel some common myths and confirm some truths about hair fibres. If you have any other questions that are not answered here, please feel free to add in the comments below with questions you would like us to research!

Hair fibres are typically divided into 2 groups; the older keratin fibres, and the newer technology cotton fibres. Since many of these answers differ between the two types, we will answer them separately.


1. “Hair fibres will stop new hair from growing”

Keratin Hair Fibres FALSE.

Hair fibres are too large to fit into your follicles and block them. Good quality hair fibres will also cling effectively to the individual hairs on your hair, rather than settling on your scalp.

Cotton Hair Thickening Fibres FALSE.

Same reasons as for keratin hair fibres, they are too large. But also, cotton hair thickening fibres have a higher cling value so they tend to stick to the hair more and therefore less seem to gather on the scalp.


2. “Hair fibres are full of harmful chemicals”

Keratin Hair FibresTRUE

All the keratin brands we’ve researched (including the old fashioned Toppik) contain some pretty nasty chemicals, the most harmful being ammonium chloride. Some of these chemicals can cause some pretty serious side effects in people who are susceptible to them, so it’s a good idea to check the ingredients of a hair fibre before using it.

Cotton Hair Thickening FibresFALSE

All of the cotton brands we’ve researched DO NOT contain harmful chemicals and tend to have a fairly natural list of ingredients, so it’s a good idea to look for a cotton fibre if you’re sensitive to chemical additives or conscious of avoiding them for any reason.

keratin hair fibres turn green in water

3. “Hair fibres go green if exposed to sun or water”

Keratin Hair FibresTRUE

We did some tests with various hair fibres by shaking them into a glasses of water. All the keratin fibres we tested (mostly browns of different brands) turned the water bright green! Leaving the keratin fibres in the sun caused the blonde keratin fibres to turn green too.

Cotton Hair Thickening FibresFALSE

All of the cotton brands we’ve tested didn’t change the colour of the water at all, even after a couple of weeks. Cotton seems to be more colourfast.


4. “Hair fibres will stain my scalp/clothes/pillowcase”

Keratin Hair FibresTRUE TO SOME EXTENT

Most of the keratin brands we tested leeched at least a bit of colour onto fabrics, though it washed out. This is probably due to being less colourfast than cotton (as tested above). As for scalp staining, we found that with any moisture, the keratin fibres did colour the scalp (sometimes green!). However, this did wash off when hair was washed.

Cotton Hair Thickening Fibres FALSE

None of the cotton brands we tested leeched any colour on scalp or fabrics, even with a little moisture.


5. “Hair fibres are itchy and irritate the scalp”

Keratin Hair FibresTRUE TO SOME EXTENT

We blind tested a bunch of keratin products and found that some people did find them to be a bit itchy and irritating. This is likely due to the chemicals used. It should be noted, however, that not everybody was irritated by them and not all products caused irritation.

Cotton Hair Thickening FibresFALSE

None of the cotton brands we tested irritated the scalp. This is probably because they are made from a natural fibre and tend to use natural colours and be chemical free.


6. “Hair fibres contain animal products”

Keratin Hair FibresTRUE

Most keratin brands do use animal products to synthesise their keratin, including wool, horns, feathers, claws and hooves. Since these animal products contain a large amount of bacteria, a significant amount of bactericides and preservatives are required which is why it’s just not possible to find an all-natural keratin hair fibre.

Cotton Hair Thickening FibresFALSE

There is really no reason for cotton hair fibres to include any animal products since the fibres themselves are derived from plants. If you are concerned about animal products and welfare in general, opt for cotton fibres and check that the company you’re buying from doesn’t test on animals.


  1. Having read the above about the Fibres is yours Cotton or Keratin?

    • Hi Jeanette, Our products are all 100% cotton.

      • Thanks for your reply. You mention serious side affects using Kertain fibres what are these? What about natural Keratin fibres? Using them on Occassion rather than everyday, Is this alright?

  2. Hi Jeanette,

    There have been some reports of reactions to ammonium chloride, the most common being asthma-like symptoms right up to nose bleeds and coma. Many keratin fibres also use DMDM Hydantoin which is a chemical which releases formaldehyde which can also cause respiratory reactions similar to ammonium chloride as well as cancer.

    Check out this government website for more information about formaldehyde exposure – http://www.cancer.gov/about-cancer/causes-prevention/risk/substances/formaldehyde/formaldehyde-fact-sheet#q3

    These side effects aren’t common and if you are using a keratin product without any problems, you’ll probably be ok. Some people are more sensitive toe chemical additives than others.

    Regarding ‘natural keratin fibres’, as far as we can find, there is no such thing 🙁 Keratin fibres are either made from animal products which need to be treated with chemicals, or synthesised from chemicals to mimic keratin.

    Hope that helps!

  3. Can you use this product if you swim and I mean swim as a competing swimmer not keeping your head above water swimmer

    • womenhairloss April 8, 2017 at 4:37 pm

      Hi Liesa, No it isn’t designed for use when swimming as it is designed to wash out. A light splash is fine as is light rain, but if you add a lot of water it will wash out.

  4. How often do you recommend to was boostnblend from hair

    • womenhairloss May 5, 2020 at 2:51 pm

      You can leave it in between washes. Your normal wash cycle is just fine. I wash mine every 1-2 days. But some women wash every 3-4 days, even longer and it is totally fine.

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