Expert: Walter Hintz - 6/18/2009

Question
QUESTION: What is the scientific basis for when we feel itchy in some part of the body, that we get this urge to scratch it, and that when we do scratch it we feel a sense of pleasure indicating that this is what the body needs. Why?  What is happening on a biological level?

ANSWER: Hi Martin;
It is thought that an itch is stimulation of free nerve endings, the skin receptors which are the pain nerve endings. Itching is therefore a mild stimulus to the free nerve endings.  Tickling also involves free nerve endings as well as touch receptors.  To some it is painful while to others it is pleasurable Scratching causes a release of histamines which increases the itching.  You may notice that when you first scratch the itching at first gets worse.  Itching is unpleasant and the scratching eventually relieves the stimulus.

---------- FOLLOW-UP ----------

QUESTION: What do you mean by "free nerve endings"?  By the sound of it it seems as if these nerve endings are self maintaining themselves through feedback in order to keep in optimum performance.  Is this what you are getting at?

Answer
The sensory neurons in skin, those that are stimulated by touch which include hot,cold,pressure, have a nerve ending that ends with a bulb while pain receptors do not but branch out covering a greater area. But they spread out and taht is why you can sick a hyodermic  or acupuncture needle into th skin without feeling pain. Because of the branching they are called free nerve endings