A friend told me that when you're sick, your hair grows faster. When I started asking a lot of questions, my friend said it's a known fact but she doesn't remember where she heard it first or what was the scientific reasoning.

Online research did not lead to any credible scientific answers that prove or debunk this. Though, it does look like that a lot of people believe in it, not just my friend.

I couldn't think of any physiological reasons for this to be true. So is it just a myth?


Does facial hair grow faster when you're sick?
Does being sick make your hair grow faster?
Apparently nails and hair grow faster when you're sick. Right? Expert opinion?
Does being sick effect the growth of your hair and nails ?
Does hair grow faster when you're sick?

  • 7
    Note that 'hair growing after death' has been debunked - the skin dries out/retracts so that e.g. beard hair stands out more. This may be the same effect.
    – user22865
    Oct 27, 2016 at 9:58
  • @JanDoggen: Obligatory plug
    – Oddthinking
    Oct 27, 2016 at 13:05
  • 1
    I found nothing about this claim when searching with German terms. It is difficult to prove its non-existence, it's basically up to your friend to prove it. You could tell her that it is known that hair grows slower when you are sick, and then wait how she reacts.
    – daraos
    Oct 28, 2016 at 11:05
  • I've never heard that claim. I may have heard that hair grows thinner during illness but don't know if that's true. I do know that fingernails grow more slowly during illness to save resources. Just based on that I'd guess hair either grows the same or more slowly.
    – A L
    Oct 28, 2016 at 22:00
  • 2
    @JackAidley Could you please provide a link to the "hair growth rates increase with temperature"-claim? I find it quite interesting, bit w haven't heard this before...
    – Arsak
    Mar 25, 2019 at 19:12

2 Answers 2


This is not a very authoritative answer but skimming through this book on The Biology of Hair Growth leads me to doubt it. It talks a lot about the limited factors which can stimulate hair growth but there is no indication that any of this could be related to common illness. To the contrary, it mentions that severe fevers can cause hair loss.


So I actually learned this from my medical science class...What happens when your sick is that your body detects a foreign suspect (a virus) that is attacking your cells to multiply. Helper T cells help activate B cells for antibodies and macrophages to kill ingested microbes. Also they help activate cytotoxic T cells to kill infected targeted cells. In a sense there is a war occurring inside your body. How does this involve hair growth? In other words, your body also detect that there is damage and it needs to be fixed pronto tonto! So basically your body then needs to create new cells to replace the infected target cells. How does your body get rid of dead cells? They get placed on your hair, nails, and skin which are all dead cells 😀 I hope this helps! Anyone please feel free to add or correct 👍

  • 3
    Welcome to Skeptics! Please provide some references to support your claims.
    – Oddthinking
    Apr 21, 2020 at 7:00
  • 8
    What medical science class taught you that hair, nails and skin are made up from dead cells from your immune system? Please provide a really good quality reference, or delete this as it isn't true.
    – Oddthinking
    Apr 21, 2020 at 7:03

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