What Are Those White Knots That Are Suddenly Appearing in My Rug?

Fine hand knotted rugs can last for generations giving those of us who are lucky to live with them plenty of opportunity to seemingly know each knot by heart.  That is why when a new white dot appears where there was once a sea of red and blue or other vibrant color, many people panic fearing that their treasured rug has fallen victim to moths.  These white dots seem to appear quite suddenly, maybe after returning from a professional cleaning.  What are the white dots that appear almost overnight in a very well loved rug?
In order to understand what a white knot is, it is important to understand the basic structure of a hand knotted rug.  One of the first steps in hand knotting a rug is to extend the vertical strands, often made of cotton, around the loom.  These vertical strands are known as the warp of the rug.  The very ends of the warp (on both the top and bottom) are what the fringes are.  Because cotton strands are often shorter than the vertical length of the finished rug, weavers tie cotton strands together to create a longer warp.  The places where the cotton strings are tied are the white knots.  When a hand knotted rug is knew, the pile yarns are long and hide these white knots.  In addition, sometimes weavers color the white knots so that they match the surrounding pile.  So why do they appear so suddenly?
The white knots become visible eventually  because, over time, the pile gets shorter as the rug is worn from every day use.  The shorter pile reveals the white knots that had once been hidden.  It is very common for white knots to be more visible after a professional cleaning because the cleaning brightens the cotton that may have been soiled from years of use (and which was soiled while the pile was still long making the knots invisible).  
Should you be worried about the appearance of white knots?  There really is no reason to be alarmed.  It is a natural part of the weaving process.  It does indicate, however, that the pile is worn down so the rug is becoming more susceptible to damage (from heavy furniture, particularly heavy traffic, for example).  But taking precautionary measures such as treating the rug a little more delicately, will extend the life of the rug. --www.traditionalrugrepair.com