="an ">&ensp;</span>and <span  title="" class="an ">&ensp;</span>chemical <span  title="" class="an ">&ensp;</span>nociception <span  title="" class="an ">&ensp;</span>but <span  title="" class="an ">&ensp;</span>is <span  title="" class="an ">&ensp;</span>not <span  title="" class="an ">&ensp;</span>essential <span  title="" class="an ">&ensp;</span>for <span  title="" class="an ">&ensp;</span>hair <span  title="" class="an ">&ensp;</span><span  title="Neuron" class="an Neuron">cell</span><span  title="" c