Tuesdays with Shlomo

Mucous membranes

Dr. Shlomo Freiman

December 19, 2023

A young kitten yawns in a patch of sunlight.

Examining your pet’s mucous membranes sounds like something of a dirty job. Unless you’ve got a particularly slobbery pooch, it’s actually not. Despite the visceral name, checking the mucous membrane is often as simple as lifting your dog or cat’s lip up an inch. Doing so can catch many potentially life-threatening conditions early, especially if you make it a habit and get to know what healthy mucous membranes look like.a

In this edition of Tuesdays with Shlomo, Dr. Shlomo Freiman breaks down what mucous membranes are, where they’re found on your pet, how to check them, and what you can learn from them. Read on to learn about one of the simplest, most important ways you can be involved in your pet’s health.

Okay, so I’ve heard people say that you could maybe find out if your dog was sick by looking at their nose or lips. I always thought it was kind of like a folk remedy, but this is actually something you can do to assess your pet’s health, it seems like? Checking the mucous membranes?

Yes, but it’s not the nose, although the lining of the nose is a mucous membrane.

So just looking at your dog’s nose doesn’t tell you anything.

A cat staring at the camera with both third eyelids visible, in the inner corners of the eyes.
Third eyelids. Image courtesy of rover.com

No. It’s not what people say — “Oh, it’s dry,” or, “It’s hot.” It’s more specific than that. Just in general, the mucous membrane is lining. It’s not skin. It’s a special kind of a tissue with special glands. For our purpose, it’s really the inner lip. So, like, the gum but also the third eyelid. It’s another part of the eyelid, the third eyelid, which we don’t have, but dogs have and cats have. It’s also lined with this type of a moist membrane, and that lining is what we’re talking about.

I want to be careful here to say that it’s not about diagnosing. Looking at your pet’s mucous membranes is more of a way to tell if things are off. It can help you assess how serious things are and how urgently you need to take care of the situation. But it is a way — a simple way, perhaps a primitive way, but nonetheless an effective way to help you assess your pet’s status. Again, it’s extra important when your patient doesn’t talk.

Yeah, it’s one more data point for you.

For me, but also for the pet parents.

I know you said it’s primitive and not to be insulting, but maybe it’s good for people who don’t have the same training as you. Maybe they can see something that might be a red flag in a way that’s very easy for them to understand. Like the color of the tissue or the moisture level.

Right, exactly. The key thing is, since pet parents are not trained and they don’t see animals all day long, they get into the habit of checking their pet regularly. You should know what it looks like when everything is normal so you get a sense of what normal is. I have the advantage of three decades of examining pets. Probably tens of thousands of animals — a lot of data. So I kind of have a sense of what is normal for any pet. But a regular pet parent doesn’t need to know all the different breeds. All they need to know is their pet.

Mucous Membrane Color Check: Dogs. Gently lift your dog’s upper lip. Look for a pigment-free spot on the inner cheek or gums. If your dog has heavy pigmentation, you can look for a clear spot on the lips or even the nose.

So if people learn about the basic signs and symptoms revealed in a pet’s mucous membrane, it can kind of serve as an early warning system? Once they’ve figured out what it looks like when it’s healthy?

Yeah. It’s not a special tool, there are no digital screens, but it is very important.

Basically, there’s some truth to the folk tales. You mentioned that there might be some differences in the way you would do this from a cat to a dog. What are those?

You can see some differences easier by looking at the third eyelid instead of the membrane in cats sometimes. I still think it’s good to look at both to get a sense of what is normal.

So when a mucous membrane doesn’t look right, what kind of things are the cues? What tips us off?

The amount of moisture is one. It can be situational though. If your pet’s mucous membranes are dry but otherwise they are perfectly fine and everything else is perfectly normal you probably shouldn’t rush to the doctor. But if the pet is a little bit under the weather or maybe their appetite is a little bit down or there are some other symptoms, you can correlate that with the mucous membrane being really dry. That may be something more serious. The color is a very big one. Maybe your cat is not breathing normally and is a little bit lethargic and you looked and the color is really a lot paler. Or maybe your cat is panting like a dog and you notice their mucous membranes are a lot more gray and blue than they should be. Maybe when you look at your dog you see little dots, red dots, and the mucous membranes are pale. All of these are very significant observations that indicate that you need to engage your vet immediately.

Mucous Membrane Color Guide. Coloration changes can be subtle and hard to evaluate, even for the pros. Use the examples below, and take your best guess at the closest color.

All of these can and should be red flags to you if you know what normal is for your pet. You don’t have to diagnose. Again, we are not trying to say, “Oh, this is what it is. That’s what it means.” Getting a diagnosis is more complicated and typically require more diagnostics. The point is not for you to become a doctor and try to diagnose your pet’s condition online..

It sounds really like that’s not the goal of the at-home mucous membrane check. The home test is just to have another data point to maybe compare with some other things you’ve observed, right? And maybe to tip you off when you need to contact your vet?


Does that then dovetail with the stuff that we’ve talked about every single time before, like telehealth? Where if you have this hunch and you see this data point and you’re like, “Oh, my pet’s gums look blue, that’s odd,” you maybe would use that online triage or call in?

Yes and it’s especially easy to do in the Felix&Fido ecosystem, where all you need to do is jump on there and say, “Hey, I think my pet has an abnormal mucous membrane,” and send a picture.

And we can be like, “Oh, no, don’t worry about that. These are normal.” Or tell you, “This is definitely important. We need to do something about it.” That’s why I like it, because you can send pictures and videos, I can review them, and I can either assure you that things are good or tell you, “No, this is a serious red flag.” Telehealth works very well in this context..

It sounds like the mucous membrane is this thing where if you’re not a professional, it’s a pretty imprecise but pretty useful thing. Like, you’re not making a diagnosis, you’re not getting a test result, but it can give you a really useful tip, basically.

And even for the professional, I’m still not making a diagnosis solely based off mucous membranes. I might be like, “Oh, okay, that looks bad.” But we still need to take X-rays or we need to put a pulse oximeter on or do blood work. So it can really give a lot of significant clues together with some other things. It’s only part of the puzzle that I think about when I try to figure out what is wrong with my patients.

Mucous Membrane Color Check: Cats. Gently lift your cat’s upper lip. Look for a pigment-free spot on the inner cheek or gums. If your cat has heavy pigmentation, you can look for a clear spot on the lips or even the nose.

I always forget how much it affects your practice that patients don’t talk.

That’s what I mean about the puzzle. You’re just seeing what fits the pet, fits the symptoms, fits the scenario, in an effort to come up with a diagnosis. If you do a puzzle, the corners and the ends are very important to begin with. You build the rest of the puzzle from there.The mucous membrane can be a very significant piece.

Like, it can maybe be a corner piece, and then from there you can figure out the rest and fill it in?


So, you’ve given some specific examples of what to look for — the moisture, the spots, etc. — but what kind of conditions are associated with those symptoms? I guess, what are the common conditions that you might catch by looking at the mucous membrane?

One is dehydration bleeding disorder.

Can they have bloody gums?

Well, it’s not bloody gums. But maybe the dots are in a pattern that can indicate a bleeding disorder. I see liver disease with gums that are shades of yellow. Sometimes it’s anemia, which means the mucous membrane is going to be pale. There are also problems with breathing and oxygenation, especially in cats. They can really be a lot sicker than people think and they just lay low and you wouldn’t know until you look at the mucous membrane and see the significant changes there. Those are the big ones.

Those are all serious conditions. Have you ever seen an animal’s gums or seen their mucous membranes and known exactly what it was?

I mean sometimes you can see that there’s this classic pattern. Like with the bleeding, those kind of dots. And you’re like hey, “This dog or this cat — usually it’s more in dogs — has a problem with their platelets.” Certain types of liver disease, especially in cats, can be identified pretty easily, especially when the mucous membrane is yellow. Again, the shades of color matter a lot, and that’s again why it’s so important for people to know what the normal range is for their dog or cat. When things really get out of that range, they can know it’s not right/ Instead of sitting on the fence and wondering whether to call a vet, they can just open our Felix&Fido chat and send us a picture. They don’t even have to think about it twice.

It’s so easy.

Yeah, exactly.

So we talked about your late cat Nile last time. You mentioned that Nile benefitted from having his mucous membranes examined once. Maybe even used up one of his nine lives?

Yeah. So this is a true story. Nile, my cat, was huge, and big cats are more prone to a condition called hepatic lipidosis. Of course it was my cat and maybe I should have caught it, but at the time I was very busy running a clinic.

That’s the nice thing about cats, you can kind of leave them alone. They do their own thing.

Yup, he’s doing his own thing. Going outside, coming in and out, interacting with us when he wants to. This was a long time ago. Our younger son was, at the time, maybe twelve or something like that. He’s really a pet and animal person and really loved that cat. He called me one day and he said, “I don’t think Nile is eating as much and I think he’s more lethargic.”

It’s kind of funny. He didn’t know what to do but said the cat’s mouth looked a little yellow. I said, “We’re going to take a picture.” Sure enough, Nile’s mouth was very yellow. I was definitely concerned. I diagnosed him with hepatic lipidosis. We had to put a feeding tube in and manage him and he was in the hospital for a week, but he recovered and did well.

So the liver disease wasn’t what killed him!

No, no, no. This was many years before we lost him. The fact that my son was able to make those observations and then tell me what the color looked like was very, very significant and we were able to reverse Nile’s liver condition and take care of it. What is the expression? The shoemaker goes barefoot? I wasn’t necessarily able to look at my cat as much as I should have, but my son was and he was able to alert me.

So the moral of the story here really is we all need to be looking in our pets mouths a lot more.

Yes, exactly.

Anytime you’re bored, just pull those jowls back?

Well, more like apart. Take a look, take a picture. You can just flip up their lip and look at the side, kind of.

You’re not like sticking your hand fully inside their mouth.

No, you just lift the side. And if you do that you just kind of get a sense for it. That’s really all you need to do. That’s it. Besides the third eyelid!

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