According to PlantCare.com, "mulch is a gardener's best friend"; however, it might not be a dog's best friend. Some kinds of mulch are dangerous to dogs.
Cedar mulch, pine bark mulch and pine "straw" (longleaf pine needles) are all widely used.
Dogs may be attracted to garden mulch because it is cool or because, in the case of cedar mulch, it contains a natural flea repellent. However, some types of mulch attract dogs due to the scent or taste of the material.
Avoid using cocoa mulch, as it contains between 54 and 847 mg per oz. of the lethal chemical theobromine and can easily poison a dog if ingested. It only takes a small amount of cocoa mulch to make a dog seriously ill.
Cedar mulch and pine mulch are nontoxic to dogs if used in their natural condition. If purchasing colored mulch, be certain that the dye is harmless to dogs or it will irritate the dog's skin or stomach if ingested.
Although a dog may not be allergic to mulch, it might be allergic to the chemicals used to keep the mulch from decaying or to prevent insect infestation. These chemicals may cause contact dermatitis---irritation associated with allergies---which may in turn cause pus-filled bumps to form on the dog's paws and stomach.
- spitz dog image by Sergey Kolesnikov from Fotolia.com