Discuss LadyDarko E.'s answer to: What makes dogs chew and
scratch?  Usually fleas.  Lady Darko  Liked this answer? Tell
your friends about it  3 Comments About This Answer  Add your
comment  Fleas can make them scratch and chew at themselves, but
so can ticks, dry skin, poor diet (dry skin), and allergies to
something in their environment.  Flea washes, treatments, and
anti-pest "flea collars" have chemicals that cause itchy rashes
on some canines.  There are also skin diseases such as mange,
fungus rash, and some skin worms (especially around the rectum)
that can cause them to scratch, chew, or lick excessively. When
in doubt, and if you can afford it, take them to a vet for
evaluation if a pink or red rash, bald spots/falling out hair,
rough/dry/"scaly" skin, bloody rashs or sores, or little white
or black "pods" at the base of individual hairs are observed
(eggs of parasites).  Some breeds need to have the fur pulled
out of their ears regularly and their ear channels cleaned
regularly to prevent infection