Bitter Taste Receptors on the Skin and in the Gut -- Nicotine Effects

(Credit: <a href="https://www.vecteezy.com/free-vector/bitter">Bitter Vectors by Vecteezy</a>) Watching this video on the history of Bitter taste receptors that are also present in the gut and on the skin got me thinking.... More questions than answers. Let me know if you have any of the answers so I can update this post! Some background to follow my thinking: Nicotine is bitter . About 10% of those who use low-dose nicotine patches ( according to our current research ) experience skin irritation . Low-dose nicotine collects at high rates in the gut when it comes from a patch -- as much as 80x compared to the amount in the bloodstream. Thus the digestive side effects even in smokers when the dose of patches is too high. Bitterness is not always bad, but evolution taught us that bitterness = danger. This is dying out in humans. The bitterness receptors in the gut don't connect with the brain directly like in the mouth. Their reaction is more local. This m...