The most popular material from which dog chews are made is from the hide of cows, horses, and other animals.  Most of these chews are made in foreign countries where the quality of the hide is not good enough for making leather.   These foreign hides may contain lead, antibiotics, arsenic, or insecticides which might be detrimental to the health of your dog...or even your children.  It is not impossible that a small child will start chewing on a piece of rawhide meant for the dog!   Rawhide chews do not serve the primary chewing functions very well.  They are also a bit messy when wet from mouthing, and most dogs chew them up rather rapidly.   They have been considered safe for dogs until recently.

Rawhide is flavorful to dogs.  They like it.   Currently, some veterinarians have been attributing cases of acute constipation to large pieces of incompletely digested rawhide in the intestine.  Basically it is good for them to chew on, but dogs think rawhide is food.  They do not play with it nor do they use it as a pacifier to relieve doggie tension.  They eat it as they would any other food.  This is dangerous, for the hide is very difficult for dogs to digest and swallow, and many dogs choke on large particles of rawhide that become stuck in their throats.  Before you offer your dog rawhide chews, consult your veterinarian.   Vets have a lot of experience with canine chewing devices; ask them what they recommend. 

Reference:    Rottweilers by Anna Katherine Nicholas    #1 Best Selling Rottweiler Book