hair loss

my 2 year old male lab has thinning hair patches along both sides of his body. any idea what this may be caused by?

You know it could actually be anything!

Allergies (environmental, food), stress, fleas, thyroid, cushings etc...

If you take a picture of it and post it we may be able to notice something else.

When did it all start? Any food/environmental changes? Do you use harmful chemical cleaners on your floors/carpets and the dogs bedding?