Nutritional Deficiencies
Your dog's body knows what it requires to function and when it's missing something essential in the diet it can cause an unusual craving for your dog to try and fill this need - for example some dogs with mineral deficiencies have been known to eat soil.
Dogs may develop nutritional deficiencies due to a poor diet. Your vet will be able to evaluate your dog's diet and may look to transition your pet onto a high quality balanced commercial diet if they are concerned about a lack of nutrients.
Gastrointestinal Disease
Pica can also be associated with poor absorption of nutrients - this can be due to chronic gastritis/gastroenteritis or a malabsorptive disorder.
Gastrointestinal disease can have a wide range of underlying causes including genetic diseases, infectious, inflammatory or cancerous disease processes.
Anaemia
Dogs with anaemia may develop Pica due to the lack of iron. Dogs can develop anaemia secondary to chronic blood loss, increased consumption of red blood cells or destruction of red blood cells. This can cause the body to crave eating unusual things to replenish the iron stores.
Teething
Teething is a normal part of puppy development and this is a common time for puppies to want to start chewing everything! Although most dogs will stop at chewing occasionally this can progress to consuming objects too.
Boredom
Dogs need mental stimulation and when bored they will find something to do. When extreme boredom sets in dogs can develop unusual habits to keep themselves occupied.
Anxiety
Dogs that are suffering from anxiety can develop strange habits as a method of redirecting their stress, in some cases this may be Pica. Dogs that have severe separation anxiety may resort to eating unusual things when their owners are out of the home.
Compulsive disorders
Some dogs may be diagnosed with a true compulsive disorder. This is when your dog has an obsession with consuming foreign objects with no other underlying cause found.