Only for hand washing in a pinch. Shampoo can clean a small item in a sink, but it isn't built for a washing machine.
Traveling without laundry detergent, or running low at home, makes the shampoo bottle in the shower look like an obvious backup plan.
It can work, but the reasons it's not a real substitute have more to do with what shampoo leaves behind than what it fails to clean.
Shampoo is built to strip oil from hair and often includes conditioning agents, silicones, and fragrance oils meant to coat hair strands and make them feel smooth. Those same ingredients can leave a slight film on fabric that doesn't rinse away as easily as a detergent surfactant does, especially on absorbent fabrics like cotton.
Like dish soap, shampoo foams heavily when agitated, sometimes producing several times more suds per ounce than laundry detergent. A washing machine turns even a tablespoon into far more foam than the rinse cycle is designed to clear, which can leave residue in the fabric or, in a full load, cause the same overflow risk as any high-foam soap.
Skip shampoos with heavy conditioning formulas, added oils, dyes, or strong fragrance on anything you want to keep smelling neutral. Clarifying or conditioner-free shampoos rinse the cleanest if you have a choice, since they are designed to strip residue rather than add it.
If the item can go a day or two before you need it, waiting for a proper detergent run is almost always the better call. Shampoo washing is best reserved for genuine travel emergencies or a single stained item, not as a repeated laundry method.
Laundry detergent is balanced for the water-to-suds ratio a washing machine actually uses, plus it includes enzymes and brighteners that shampoo has no reason to contain. A full load of laundry also needs a cleaner that rinses predictably across many garments at once, which is exactly what shampoo, formulated for a single head of hair under running water, was never designed to do.
Shampoo can rescue a single dirty shirt when there's truly nothing else on hand, but it's a one-time fix, not a laundry room staple. Regular detergent still rinses cleaner and handles a full load the way a washing machine expects.
It can if you don't rinse thoroughly. Shampoo's conditioning ingredients are designed to cling to fibers, so plan on two or three rinses instead of the one you'd use with detergent.
A small amount of a gentle, fragrance-free shampoo can work in an emergency, but a dedicated delicate detergent is still the better long-term choice for fibers like wool or cashmere.
Baby shampoo tends to have fewer added oils and lighter fragrance, which makes it rinse a bit cleaner from fabric, but it still isn't a substitute for actual laundry detergent.
A small amount of bar soap shavings or a travel detergent sheet rinses more predictably from fabric than shampoo and is worth keeping on hand for trips.