What Causes Shinny Clumps In Hair?

I have been finding a few 4-6 little tiny white shinny clumps in my daughters hair on in off for the past 2 years, They are stuck to the hair shaft but easily fall apart when i rub them in between my fingers. I always pick them out and treat her for lice assuming that is what it is. I have never seen an alive bug in her hair and her head does not itch and no one else in the house seems to ever catch it. I am going crazy thinking how does she keep getting lice, she is 14 years old, buy now I read about hair casts could it be this?