OnceletMilk tells you when it has gone off. Most things don’t. A bottle of sunscreen looks the same in its fourth summer as in its first, and a tyre can look fine for years after it has started to age. Here are the common ones, what official sources say, and how to find the date that matters.
The short version
| Item | Lasts about | Source |
|---|---|---|
| Sunscreen | Until the printed date, or 3 years from purchase if there is none | FDA |
| Mascara | About 3 months after purchase (makers say 2 to 4) | FDA |
| Child car seat | Until the maker’s expiry date, usually 6 to 10 years from manufacture | NHTSA, AAP |
| Car tyres | Some makers say replace at 6 to 10 years, whatever the tread | NHTSA |
| Carbon monoxide alarm | Check the date on the unit; USFA’s checklist says under 7 years | USFA, CPSC |
| Smoke alarm | 10 years from the manufacture date | USFA, NFPA |
Sunscreen: 3 years if there is no date
Sunscreen is regulated as a medicine in the US, so it has stricter rules than cosmetics. The FDA requires an expiration date unless the maker has shown the product stays stable for at least three years. If your bottle has no date, treat it as expired three years after you bought it. If you don’t know how old it is, the FDA’s advice is simple: throw it out.
Mascara: about 3 months
There is no US law that makes cosmetics carry an expiry date. For eye make-up, the FDA still advises throwing mascara away three months after purchase, and notes that makers usually say two to four months. Stop using any eye cosmetic straight away if it irritates your eyes, and replace it after an eye infection.
Child car seats: check the label
There is no legal expiry date for car seats in the US, but manufacturers set one, usually 6 to 10 years after the date of manufacture. Check the label or the manual. The seat should have a label with its date of manufacture and model number. You need both to check for recalls and to know whether the seat is too old. NHTSA also recommends replacing a seat after a moderate or severe crash.
Tyres: age you can’t see
Rubber ages with time, heat and sunlight, not only with miles. NHTSA warns that you can’t tell a tyre has aged just by looking at it. Some vehicle and tyre makers recommend replacing tyres that are six to ten years old, however much tread is left. Cars that sit a lot and spare tyres are most at risk, because they rarely get replaced.
To find a tyre’s age, look for the DOT code on the sidewall. The last four digits are the week and year it was made: “0322” means the third week of 2022. The code may only be on one side.
Carbon monoxide alarms: they wear out too
The sensors in CO alarms don’t last forever. The U.S. Fire Administration’s home safety checklist asks whether your carbon monoxide alarms are less than 7 years old, and older CPSC advice said every five years. The most reliable answer is the replace-by date printed on your alarm. The CPSC also recommends testing alarms monthly and changing batteries once a year, unless the alarm has a sealed 10-year battery.
Smoke alarms follow the same idea with a 10-year life. There is more on those in How often should you replace it?
The manufacturer’s date wins. These are general rules. If a label or manual gives a different date for your product, go by that.
Write down the start date
All of these have one thing in common: the clock starts on a day nobody remembers. The day you opened the mascara, bought the sunscreen or fitted the tyres. Once that day is written down, the rest is counting.
That is what Oncelet does. Tap once when you open a new tube or fit new tyres, and it shows how many days it has been. You can set a reminder so the next replacement doesn’t sneak up on you.
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- U.S. Food and Drug Administration. Sunscreen: How to Help Protect Your Skin from the Sun.
- U.S. Food and Drug Administration. Cosmetics Safety Q&A: Eye Cosmetic Safety and Shelf Life and Expiration Dating of Cosmetics.
- NHTSA. Used Car Seat Safety Checklist and Car Seat Use After a Crash.
- American Academy of Pediatrics. Car Safety Seat Checkup, HealthyChildren.org.
- NHTSA. Tire Safety and Tire Buyers’ FAQ (PDF).
- U.S. Fire Administration. Fire Safety Checklist for Homeowners and Renters (PDF).
- U.S. Consumer Product Safety Commission. CO Alarms.