HOUSTON -- We check the expiration dates on milk, food and even sun block. But did you know some manufacturers say your child's car seat can also expire?

Some viewers asked KPRC Local 2 investigative reporter Amy Davis why seats expire and if it's a true safety concern or just a way for manufacturers to make more money.

Esmeralda Cervantes e-mailed us when she said she realized her son's car seat had expired.

So how did she know? Most manufacturers put expiration dates on the side or the bottom of the seat on a label.

Most labels read that seats typically expire anywhere between five and 10 years.

Granted, most toddlers will outgrow their safety seats long before the expiration date, but manufacturers realize seats are handed down or sometimes sold second-hand.

What causes a seat to expire? Some safety groups suggest that the plastic base of car seats can break down over time from repeated exposure to extreme heat and cold.

But the National Highway Traffic Safety Administration told us the real concern is constantly changing regulations and standards.

NHTSA recommends discarding all safety seats six years after the manufacture date. The federal agency also recommends replacing any car seat that is involved in a major accident.

Cervantes wants to toss her son's seat, but she wanted to know the best way to do that so it wouldn't end up in a thrift store and get reused.

Some groups recommend cutting the harness straps or cutting up the cover so that it's clear the seat is unusable.

For more information on child safety seats, check out the following links.

NHTSA: Child Seat Information
CPSafety.com
American Academy of Pediatrics: Car Safety Seat Guide

What about expiration dates on car tires, bottled water and bike helmets? Check out the Ask Amy blog for details.