Only in recent years have I befriended the feline species. I was always a ‘dog person.’ But in the past five years or so, I've had just as many feline roommates as human roommates, and I've grown to love the little furballs.

Ironically, since I have developed an affection for cats, I've also become allergic to them. Thanks to environmental control measures, my cat allergies are not very bothersome. I've spent a lot of time learning how to avoid cat allergens in the home; the key is to always keep the cats out of the bedroom. I keep the bedroom sealed off and keep my AllerAir air purifier running at all times. (When I do have reactions, it's usually because a fur-covered blanket is brought in from another room; to avoid this, use Allersearch Allergen Wash laundry detergent to denature allergens, and make sure that you have a durable, washable hypoallergenic blanket.) To learn more about environmental controls for cat allergies, see An Allergy Sufferer's Guide to Living with Cats.

Today I'd also like to discuss a different topic related to cats and environmental control: the litter box. Cute as they are, cats frequently spread disease to humans. In fact, about half of the world's population is infected by the common cat parasite Toxoplasma gondii. This ABC News article suggests that T. gondii subtly affects the human personality and may be linked to schizophrenia. Other studies suggest that the parasite may play a role in bipolar disorder, depression, and anxiety. Oxford University researchers say that high levels of the parasite lead to hyperactivity and lower IQs in children.

So how do people get this parasite? Well, it comes from cat poop, particularly the poop of cats who venture outdoors and eat infected animals. About 80% of domestic cats are infected. Clean out the litter box every day to avoid infection. This is crucial. After the cat poop sits out for longer than a day, the microscopic oocysts (spores) become infectious and can easily be inhaled or ingested without your knowledge. Use gloves and wear a mask when emptying the litter box. Wash your hands thoroughly after emptying the litter box, and try to keep the box in a low-traffic area of your home.

Pregnant women should be especially careful to avoid litter boxes. A woman who gets the infection, known as toxoplasmosis, during pregnancy can transmit the parasite to her child, and studies suggest that this increases the risk of mental disorders in the child. Toxoplasmosis can also cause stillbirth. Pregnant women should also avoid eating raw meat and gardening with bare hands, as these activities could also lead to infection.

T. gondii oocysts can remain infectious for up to 18 months, so it's important to thoroughly clean the area around the litter box. I recommend a HEPA vacuum cleaner, vapor steam mop, and safe, eco-friendly disinfectant. I also have an air purifier near the litter box at home (which is hidden inside a hallway closet).

The litter itself can cause health problems, too. Have you ever coughed after inhaling a cloud of kitty litter dust? That's probably because the litter contains irritating crystalline silica, a known carcinogen. (Again, you should always wear gloves and a mask when changing the litter!) If the litter bag warns that you should go to the emergency room if you accidentally swallow it, then you can assume that it's toxic. Most stores now sell the non-carcinogenic natural kitty litter. I've been using all-natural, dust-free pine pellets along with the Naturally Fresh Pet Crystal to help with odor control.