We had a grown cat and a grown dog for years. Once a week I would break a raw egg into a bowl of milk and set it on the floor for them.
The cat would lap up as much as he wanted, then the dog would trot over; she would slobber down the rest.
Today, however, I read something on the Internet saying that raw eggs and milk are both bad for cats (and perhaps dogs). I had given them the mixture for their fur; they always had healthy, glossy coats. Should I have hesitated?
Milk is not terribly digestible for mammals (including a lot of humans) past babyhood, but it isn’t as though you were feeding them antifreeze or rat poison. As for the eggs: canids, at least, will eagerly seek out and eat raw eggs whenever they can get them in the wild. I’m sure they wouldn’t do that if it were deleterious.
Eh. Everything in moderation.
Raw eggs and milk may be considered “bad for” pets for lots of reasons. You can mitigate most of those reasons by just not giving them to your pets very often.
As to the glossiness or otherwise of their pelts, what else were you feeding them? Coat health is usually just a mirror of overall health.
I used to give a beaten raw egg once a week to my dog when I was a kid to make her coat shiny. I got a dog 2 years ago and my vet was adamant that we don’t give it a raw egg and said that dogs can get salmonella too. Dogs often have trouble digesting milk products so I also stay away from those. You can cook an egg and feed it to your dog and that shouldn’t be an issue.
You should never give raw egg whites to cats. It interferes with their absorption of certain nutrients.
And cats are generally lactose intolerant.
We gave them conventional pet foods, including “dog & cat” foods (canned). They both liked them, including Heart Balls.
Sometimes–not always–we treated them to whatever meat dish we were having–beef, pork, chicken, fish. Archie, the cat, particularly enjoyed halibut, which we would have now and then–it cost more than most fish.
When we were kids we had a small calico cat named Jo-Jo. She would eat any kind of people food–even candy, cereal, cake, ice cream! And she would eat canned dog food. She would NOT eat cat food!
Lots of cats love dog food. It’s the equivalent of people eating Doritos. Cats cannot survive on dog food; it is too low in protein and does not have taurine.
It’s avidin, which ties up biotin. Might not be an issue, depending on the quality of the rest of the diet.
Egg Science and Technology, Fourth Edition
Right. Dogs can produce taurine themselves, cat’s can’t. Dogs can survive on a vegetarian diet (unhappy dogs I’m sure), but not cats.
Jo-Jo probably got her taurine from the people food she ate. (My Dad used to fish off the Santa Monica Pier; Jo-Jo also liked fresh fish.)
And lots of dogs love cat poop! I can see a Human Centipede-type situation arising. 
BARF!!
Too much fish is also bad for cats. 
As it contains too much thiaminase, and causes thiamine defficiency in them (neurological signs).
“Too much.” She didn’t eat “too much” of anything. After all, she was a rather small cat.
While we’re on the subject, I love Jelly Belly jelly beans. Whenever I eat them, Gunner the Great Dane wants one and I oblige him (because he’s my buddy and I’m a softee). Does an occasional jelly bean cause any problems for dogs?
While recommended against a few jelly beans won’t hurt a Great Dane. I recall one website that said dogs could eat fructose and a lot jelly beans will be made with that.
“Too much” in the sense of “it makes up most of the diet”. There are cases where animals are eating, well given, as in the wild they’ll go for variety, a specific type of food as most of its diet, and this causes nutritional problems.
Carnivores fed mostly red meat, with no bones, no organ meats: Increased risk of calcium/phosphorus imbalance, weak bones, fractures.
Carnivores fed mostly raw fish, particularly some species (fresh and salt water): Increased risk of neurological signs, as they contain thiaminases.
Herbivores fet lots of pasture/greens high in oxalates: Renal failure
There are others, but this is just a basic sample.
Compared to those, occasionally giving milk to adult pets (lactose intolerant) and feeding raw eggs (Salmonella risk) are relatively minor problems. But they’re not completely safe treats to give to the pets.
ASPCA page detailing what dogs and cat can and cannot eat. They even have an app.
To KarlGrenze: Jo-Jo ’ s diet was varied. She did not eat a great deal of any one thing, fish included. She ate a wide variety of food, people food–remember, she would not eat cat food. She had three litters of kittens and raised them normally; seven kittens in all. They were healthy too. 
I have a cat that will eat donuts and french fries (no, we don’t give them to her, if she has the opportunity, she’ll steal them), but won’t eat dry cat food. Only the canned. Cats are weird.
ETA: shame on you, dougie, you know the rules! Where are the pictures?