So glad I happened across this feed! 13 weeks post-partum female here. I too have also been experiencing the same rust-coloured stains on my hands and today went to my GP to discuss them. Interestingly before reading this post I suspect I have a thyroid issue. My doctor seems to think my TSH levels are within the "normal" range but I went to a talk by a Dr recently who said that thyroid should be tested against your own "normal". Not just a scale. Here in NZ they only test for TSH, but really they should test for T3 and T4 panels to get a fuller picture. I wonder if everyone here is experiencing symptoms of hypo/hyper thyroidism which then leads to the carotene hypothesis resulting in the staining. A lot of people have mentioned thyroid issues already.
My GP also suggested anyone taking B supplements may present with discolouration.
We didn't delve into it further but she mentioned something to do with Diabetes too.
I also wondered about the liver because jaundiced originates from the liver. Maybe our bodies are in excess of a certain heavy metal toxin, and it is presenting as patches on our hands. We are exposed to heavy metal toxins everywhere, vaccinations, our water, the environment etc. I personally have not had the covid vax but have been vaccinated my entire life.
For me I read the beta carotene thing and discounted it, but I will observe my diet and see how that tracks. I have ruled out any cosmetic/hygiene products.
The allergy theory is an interesting one, maybe it is a histamine response. I have been breaking out in patches of eczema, as I did post-partum in my last pregnancy, and it was a histamine response to a lot of food groups. Turns out my liver functions were Elevated and a liver detoxification diet & supplementation for 2 weeks fixed it. I didn't have the staining then however.
Anyway, GP has ordered lots of bloods so the investigations continue.