Generally speaking, most hair products have a shelf life of three years when left unopened. Lisa Silliker, director of management at haircare brand Pai-Shau, told PopSugar that once you open and start using shampoos and conditioners, “they are exposed to contaminants that will start the bacteria growth process.”
Now that we know the shelf life of hair products, how can we tell that they’ve gone bad apart from the usual time frame and an expiration stamp? Vince Spinnato, cosmetic chemist and founder of TurnKey Beauty Inc., told Real Simple that you have to pay close attention to how the product looks, feels, and smells. “The color, texture, and smell of a shampoo will change to the point that it doesn’t look or smell right,” he noted. Meanwhile, Dr. Jim Leahy, professor of chemistry and molecular medicine at the University of South Florida, shared with WXYZ Detroit that expired hair products usually have “solid clumps” that may transfer to your locks when used. “If it’s solidified like that, now you’re gonna have those chunks of whatever it is in your hair,” he said.