If a parent reports ongoing problems with nits without ever seeing a louse, it may be a sign of confusion in determining nits versus common hair debris.  This debris is often referred to as DEC plugs and hair casts.

DEC plugs (desquamated epithelial cells) may occur when oil glands in the scalp work to compensate for the drying effects of chemical treatments.  They are bright, white, irregularly shaped clumps of fat cells stuck to the hair.

Hair casts are thin, elongated, cylinder-shaped segments of dandruff which encircle the hair shaft and are easily dislodged.

A Nit (Louse Egg) is a smooth, oval shaped structure which is attached to the side of the hair shaft ranging in color from off-white to brown and is slightly smaller than a sesame seed.  Nits are always the same shape; they are never irregular, fuzzy, or encircling the hair (although the glue that the louse produces may be seen to encircle tightly around the hair shaft).