Dogs and cats have rods and cones in their retinas but in a different proportion than in the human retina. Although they can differentiate colors, what they see is likely a more muted version of what we see. Dogs, especially, probably see more shades of gray than they do all of the individual colors.

Cats, by the way, can concentrate small amounts of light in their eyes, which allows them to see at night when the rest of us have difficulty. This special talent gives them their extraordinary night hunting vision.

Hair shedding is considered a sign of health in the cat - sick cats don't shed. Although the excessive hair around the house can be a nuisance, consider it a sign of your cat's good health. To reduce the amount of hair shed on furniture and your household surroundings, comb your cat daily with an appropriate comb or brush. Your veterinarian can recommend one of the many types that is suitable for your cat.

Cats, as you're witnessing, have a much more sensitive vomiting reflex than we do, so it isn't unusual for cats to vomit when they don't appear sick. I assume your cat has a healthy, but not excessive, appetite; isn't losing weight or acting lethargic; doesn't have diarrhea; and that parasites have been ruled out. If any of these symptoms are present, or if he's vomiting green or orange liquid (bile), a medical problem is likely and should be investigated.

The two most common scenarios in which well cats vomit are (1) from eating too much or too fast, which results in vomiting undigested food very soon after eating, and (2) hairballs, which usually cause vomiting of the hairball itself. Hairballs have no sure-fire remedy, but the most popular thing to try is a hairball lubricant (make sure you give this on an empty stomach, not with food); also frequent combing, brushing, or even a "lion clip" (for a long-haired cat) will be helpful. Any hair you can remove is hair that your cat will not end up swallowing. There is also a new hairball formula cat food on the marketthat may help. Ask your veterinarian about this.

As for eating too much or too fast, this problem is usually worse in cases where cats have their food taken away and are only permitted to eat at certain times of the day, causing them to gorge when food is available. Trials of different brands of food may help. Anything else you can do (portioning the food out gradually, for example) to encourage eating smaller amounts frequently might also be helpful. If the vomiting is daily, you might want to try medication. However, most people don't want to medicate their cats daily if vomiting only occurs once a week or less.

If these ideas don't help you, the only way to get a certain answer as far as any medical cause, such as inflammatory bowel disease, would be to have biopsies of the stomach and intestinal tract done. Your veterinarian can tell you more about this.

A cold, wet nose is one sign of good health in dogs and cats. However, even a healthy pet can have a warm, dry nose on occasion. On the other hand, really sick pets can also have cold, wet noses. What does all this mean? Simply that any one indicator of health is not 100 percent accurate all the time. Sick pets with cold noses should be seen by your veterinarian. And by the same token, pets with warm, dry noses that are showing other symptoms such as lethargy or not eating should also be seen by a doctor.

I have four cats and two dogs. Until recently, I have had them vaccinated regularly. Please let me know what you would recommend to someone who has cats and dogs and wants to keep them safe but does not want to either endanger them or spend money unnecessarily.

The veterinary profession has spent the past six to seven years reexamining and discussing vaccine duration of immunity and revising vaccination protocols accordingly to make sure that companion animals get care that is tailored to their lifestyles. The goal is to make sure that an individual’s vaccine protocol is protecting them from risks they face, without vaccinating unnecessarily.

For example, in our practice we ask cat owners to describe whether their cats ever go outdoors or whether they are exclusively indoors and what other animals they might come in contact with. If a cat is exclusively indoors, we design a different vaccine protocol than if it goes out regularly or “escapes” with any frequency. Dogs that go to boarding facilities, grooming parlors or doggie daycares will have different recommendations than dogs that do not. The days of designing a single vaccine protocol for an entire species are over.

Good communication is the best tool in designing protocols that are proper for your pets. I suggest having a discussion with a veterinarian in your area, giving all of the information you know about your pets’ lifestyles. With that information, your veterinarian can explain what vaccinations he or she would recommend, at what frequency and why. At that point you can make an informed decision on a vaccination protocol designed specifically for your pet.

For more information, visit the Pet Care Library Vaccinations article.

This question was answered by AAHA member Dr. Merry Crimi of Gladstone Veterinary Clinic in Milwaukie, Oregon

My veterinarian has recently started promoting monthly heartworm preventive tablets for my dog and cat. I've also heard that the heartworm medicine used long term may be a greater risk to my pet's health. What should I do?

Heartworm disease is a serious but preventable condition. Whether or not your pet belongs on preventive medication depends a lot on the incidence in your area. We're not presently aware of any literature that notes serious risks or side effects of the preventive medicine. However, your veterinarian will take into account any other problems your pet has before prescribing the drug. Healthy kidneys and normal liver functions are essential in metabolizing most medications. For both dogs and cats, a heartworm blood test must be done before any preventive medications are given.