How Often to Replace Common Household Items
Some household items wear out quietly. A toothbrush still looks like a toothbrush after six months, and a smoke alarm still beeps when you press the button after twelve years. Below are the replacement intervals that health and safety agencies actually recommend, plus a simple way to remember when you last did each one.
Quick reference
| Item | Replace | Source |
|---|---|---|
| Toothbrush or electric brush head | Every 3 to 4 months, sooner if the bristles are frayed | American Dental Association |
| Contact lens case | At least every 3 months | CDC |
| Mascara | 2 to 4 months after purchase | FDA (citing manufacturers) |
| Sunscreen | By its expiration date, or 3 years after purchase if it has none | FDA |
| HVAC air filter | Check monthly, replace at least every 3 months | ENERGY STAR |
| Smoke alarm | Every 10 years (test monthly) | NFPA |
| Carbon monoxide alarm | On the manufacturer's date, commonly 5 to 7 years | NFPA |
| Child car seat | By the expiration or useful-life date on its label | NHTSA, manufacturer |
| Fridge and pitcher water filters | On the manufacturer's schedule (often by gallons or months) | Manufacturer |
Bathroom and personal care
Toothbrush: every 3 to 4 months
The American Dental Association recommends replacing your toothbrush (or electric brush head) every three to four months, or sooner if the bristles are visibly frayed. Worn bristles don't clean as well. Many dentists also suggest a fresh brush after a cold or other illness.
Contact lens case: at least every 3 months
The CDC recommends replacing your contact lens case at least once every three months. Germs can grow in a case even when it's cleaned properly, and contaminated cases are linked to serious eye infections. Rinse the case with fresh solution, never tap water, and let it air-dry upside down.
Mascara and eye makeup: 2 to 4 months
U.S. law doesn't require cosmetics to carry expiration dates. The FDA notes that manufacturers commonly recommend throwing out mascara two to four months after purchase, because each use can carry bacteria into the tube. Replace it sooner if it dries out or changes smell, and right away after an eye infection. Never thin dried mascara with water or saliva.
Sunscreen: check the date
FDA rules let a sunscreen leave off an expiration date only if testing shows it stays stable for at least three years. So if your bottle has a date, follow it. If it doesn't, write the purchase date on it and replace it after three years, or sooner if it has been left in a hot car or has changed color or texture.
Safety equipment
Smoke alarms: test monthly, replace at 10 years
The National Fire Protection Association recommends testing smoke alarms monthly and replacing them when they're 10 years old. The sensor degrades even if the test button still works. The manufacture date is printed on the back of the alarm.
Carbon monoxide alarms: by the manufacturer's date
CO sensors have a shorter life than smoke sensors. NFPA says to follow the manufacturer's replacement date, and many models are built to last 5 to 7 years. Most newer units chirp an "end of life" warning, but don't wait for it.
Child car seats: by the label
Car seats have a useful life set by the manufacturer. U.S. labels must show the date of manufacture, and the manual or label shows how long the seat can be used. NHTSA's used-seat checklist also says not to use a seat that has been in a moderate or severe crash, has missing labels, or has an open recall.
Around the house
HVAC filter: check monthly
ENERGY STAR recommends checking your heating and cooling filter every month and replacing it at least every three months. Homes with pets or heavy dust may need monthly changes during peak seasons.
Water filters
Refrigerator and pitcher filters are rated for a set number of gallons or months. Past that point they stop removing what they claim to. Check the model's manual. Many fridge filters are rated for about six months, and pitcher filters are often rated for around two months of typical use.
Kitchen sponges and dish brushes
No agency sets a fixed interval, but sponges hold moisture and food particles that bacteria love. Let them dry between uses, sanitize them often, and replace them when they smell or start falling apart. Many households simply swap them weekly.
How to remember when you last replaced something
The hard part isn't knowing the interval. It's remembering whether you changed the filter in March or in May. A few habits help:
- Write the date on the item. A marker on the filter frame, the sunscreen bottle or the back of the smoke alarm settles the question later.
- Log when you actually did it, not when it was due. If you replace a toothbrush two weeks late, the next one is due three months from the real date, not the planned one.
- Bundle jobs. Replace the toothbrush, contact lens case and HVAC filter on the same weekend each quarter, so one reminder covers all three.
- Keep spares. A spare filter or brush head in the cupboard removes the "I'll do it when I buy one" delay.
Frequently asked questions
How often should you replace your toothbrush?
Every three to four months, according to the American Dental Association, or sooner if the bristles are frayed.
Do smoke alarms expire?
Yes. NFPA recommends replacing smoke alarms 10 years after the manufacture date printed on the back, even if they still pass a test.
Does sunscreen expire?
Yes. Follow the expiration date if there is one. If there isn't, FDA rules mean the product is designed to stay stable for three years, so replace it three years after purchase.
How often should I replace my contact lens case?
At least every three months, according to the CDC.
Sources
- American Dental Association: Toothbrushes
- CDC: Preventing eye infections when wearing contacts
- FDA: Shelf life and expiration dating of cosmetics
- FDA: Sunscreen, how to help protect your skin from the sun
- ENERGY STAR: Maintenance checklist
- NFPA: Smoke alarms
- NFPA: Carbon monoxide
- NHTSA: Used car seat safety checklist