Dr. Phillip Tierno

Dr. Phillip Tierno is the author of The Secret Life of Germs and the director of New York University's microbiology department. He says that sponges and dishrags can hold literally billions of bacteria, so they should be kept no longer than one month.

"You tend to build up debris, food particles and fibers that you cannot eliminate," he explains. "If you de-germ by using a good household disinfectant after each use, you probably could use the sponge longer than a month."
Kitchen sink germs

"The kitchen sink is the dirtiest place in most peoples' households," says Dr. Tierno. "If you were to drop a carrot into your toilet, that toilet would probably be so clean in comparison to your kitchen."

Dr. Tierno explains that most people put meat carcasses and food debris in their sink, and the bacteria starts to build up. By using a germicide and a brush to clean, it's possible to reduce the number of bacteria.
Dust mites

Dust Mites
"Most people have dust mites," says Dr. Tierno. "They live off the skin cells that you slough off." The average person sloughs off a million and a half skin cells per hour doing ordinary things like turning over in bed. These creepy-crawly critters can lead to health issues including allergic reactions, dermatitis and respiratory problems.

The best way to ward off dust mites? Frequently vacuum textiles like your mattress, carpets and draperies. In extreme situations, a chemical called benzyl benzoate can be used to kill the dust mites.
Dust mites in bed linens

Another way to control the number of dust mites is to keep bed linens clean. Washing sheets and pillowcases weekly (use 150-degree temperature) is a must. Replace pillows every one to three years, too.

"If you can," adds Dr. Tierno, "Put an impervious cover between your mattress and your pillows. That prevents dust mites from coming into contact with your face."
Clean out freezer

In Your Freezer
How often do you clean out your freezer? Dr. Tierno says you can keep something in your freezer for six months but no longer than a year.

Everything should be sealed appropriately—vacuum sealed if possible—to prevent freezer burn. When cooking meat, make sure it is cooked thoroughly at a high temperature to kill off any micro-organisms.
Plastic bags

Plastic Bags
They say we're a throw-away-society but should you wash out and re-use plastic bags?

Dr. Philip Tierno says most plastics today are biodegradable. When it comes to re-using a plastic bag, it depends on what was in the bag first. If you have meat, meat products or cheese in the plastic bag, throw it away after one use. You may use the bag more than once if fresh produce was in it first—provided you thoroughly wash and dry the bag. Throw the bag away if the food previously in it was moldy or if there are any holes or tears in the bag.
Throw out old medication

Old Medications
Medications should be thrown away one to two months after their expiration dates. Dr. Philip Tierno says many medications change their chemical formulation in the presence of heat over time. Antibiotics are dangerous to take after a period of time and lose their potency. Never share medication that has been prescribed to you.
Old running shoes

Smelly Shoes
We love a broken-in pair of running shoes, but would you put your nose to them? Dr. Tierno says, "If something stinks, you know that you have germs growing." Old shoes serve as a breeding ground for bacteria such as staph and that causes the odor.