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If a razor cuts only the hair, then how does hair thicken and become more rough with a razor shave and not after one using a trimmer? If both are used for hair removal, why is there a difference in hair growth?

I have been using a trimmer for 1 year, but the growth of hair remained unchanged. When I started shaving with a razor, the hair growth thickened.

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  • $\begingroup$ lifehacker.com/5873922/…, and under skin and hair in this page en.wikipedia.org/wiki/List_of_common_misconceptions $\endgroup$ – Satwik Pasani Nov 29 '14 at 13:26
  • $\begingroup$ This is a myth and your evidence is purely anecdotal - voting to close as not on topic. Might suit skeptics.se $\endgroup$ – rg255 Nov 29 '14 at 20:22
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    $\begingroup$ This question appears to be off-topic because it belongs on skeptics $\endgroup$ – rg255 Nov 29 '14 at 20:23
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    $\begingroup$ May I ask how this belongs in Skeptics? It is a question seemingly based in biology that has a biological answer... $\endgroup$ – Samuel Barnett Nov 30 '14 at 20:06
  • $\begingroup$ @SamuelBarnett Because the question is based on a flawed premise. It's a myth, a wives tale, that hair does this. Before it is possible to answer a question of why something happens we should first have reason to believe it happens. We know that it doesn't so there is no question of why it does happen. $\endgroup$ – rg255 Nov 30 '14 at 20:28
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Hair does not grow back thicker when it is cut. This is somewhat of an optical illusion because when you shave with a razor it leaves the top of the hair flat rather than pointed so it appears thicker. For instance see this picture:

Hair being cut

As you can see the hair is tapered at the top and when cut loses this taper to leave a large cross-sectional area. I would say that for your question with with the trimmer that it is probably cutting the hair further up the taper where the hair is 'thinner' to begin with. A razor cuts closer to the base and thus gives a thicker appearance.

Evidence: http://www.scientificamerican.com/article/fact-or-fiction-if-you-shave-or-wax-your-hair-will-come-back-thicker/

http://www.sciencedirect.com/science/article/pii/S0190962299701817

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    $\begingroup$ could you provide a source for A) a hair being tapered as in the diagram, and B) cutting it flat makes it appear thicker then when tapered. $\endgroup$ – rg255 Nov 30 '14 at 16:43
  • $\begingroup$ could you summarise the important findings of the paper - its behind a paywall $\endgroup$ – rg255 Nov 30 '14 at 20:33
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    $\begingroup$ @GriffinEvo I am sorry my institution automatically passes me through paywalls so I didn't realise. I will sum it up in the morning as it is getting quite late here. $\endgroup$ – Samuel Barnett Dec 1 '14 at 0:15