Editors note: Responses to questions received in my inbox are sent directly to the sender. Each week I plan to choose an interesting question to answer in more detail as a blog post.

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Here is the question for the week: “What causes the third eyelid on a cat to be visible?  Is it cause for concern?  If it means the cat needs help, what should the owner do (at home, i.e. other than taking the cat to the vet)?

It’s surprising how many pet owners are not aware that their cat or dog even has three eyelids. The reason, of course, is this “extra” eyelid that people do not have normally stays tucked away behind the lower eyelid near the nose. Most of the time it stays there just doing its job of producing tears and helping keep the eye moist. Sometimes third eyelids protrude out over part of the eye and catch the attention of their people. This may or may not be cause for concern if the eyes appear normal otherwise.

The first thing you can do at home if your cat’s third eyelids suddenly become visible is to check for tapeworms. For some unknown reason the two are often seen together. Just take a look under the tail and look for small, tan-colored “rice kernels.” Or, you may find white, live segments still moving in the stool if you’re lucky. But, keep in mind that not finding any segments does not rule out the possibility. Your vet can perform a fecal exam and, in some cases, may recommend giving a treatment for tapeworms as a precaution. Because fleas are an intermediate host for tapeworms, flea control is the best way to prevent tapeworm problems.

Other causes for abdominal discomfort in cats may be behind the appearance of those third eyelids. Anything, such as changing to a new food or viruses or infections or even cancer, could cause enough pain to trigger the eyelids to come out from hiding.

The good news is many times the condition is temporary and will clear up on its own in a few days or weeks, even if the real cause remains unidentified. When that is the case, it’s been referred to as “Haws Syndrome.” The scientific name for the third eyelid is nictitating membrane. Then, there is a common name you don’t hear much describing them as the haws.

The takeaway is to know your cat well. Suddenly visible third eyelids are a clue to pay close attention. One of my favorite acronyms is “ADR” which stands for “Ain’t Doin’ Right.” It simply means you know something is out of the ordinary, even if you can’t quite describe what it is. A combination of visible third eyelids and “ADR” means it’s time for a check up at the vet’s office.