If your dog is retching a vet should be consulted as soon as possible. Labs are prone to eating and chewing all sorts of rubbish. If he vomits, pick some of the vomit up in a tissue and take it with you to the vet for analysis....it may be poisonous. My lab made himself very sick by eating some blood and bone fertilizer from the garden flower beds. Labradors have very acute sense of smell and are attracted to anything with a bone content as well as blood in various forms from various sources. They will also pick things up on their exercise walks. Be especially mindful of the urgency if the vomit contains what appears to be blood. I urge you not to be complacent as this could be very serious.