Elizabethan collars are very handy when your dog has a wound that shouldn’t be touched. Most commercial ones are made of plastic and are effective, but extremely uncomfortable for your dog. They can hinder their ability to eat and drink. If you get stuck, here’s how to make one yourself.
You can also make one simply, and quickly, with a bath towel (for larger dogs, like our greyhounds) and duct tape. Take a bath towel and fold it lengthwise in 1/4s or 1/3s depending on the length of your dog’s neck. The object is to have it cover the neck from just behind the ears to the shoulder. After folding lengthwise, fold the towel in half. Wrap it around the neck, making sure it’s snug enough to not slip forward over the head, but not so tight as to be uncomfortable. Secure with duct tape (or vet wrap, or as I have done, with Velcro One-Wrap, available in most craft stores).
For smaller dogs try using a door draft sausage and attach to their collar.