Oh, do I itch. And now, we know the gene & receptors for a non-standard kind of itch. There is an obvious advantage (if one goes in for that kind of just-so-story) to having a response to irritants. Yet there are plenty of us who over-react. In this case, the specific receptor MrgprD is expressed by a particular sensory neuron which only innervate the skin. They respond to various stimuli, including heat and noxious mechanical stimuli, but not to histamine. This means that the itches that don’t respond to standard anti-histamines could be a result of this pathway. Oh heaven. Oh joy.