A polystyrene box can be washed and reused, but the decision does not rest on the material tolerating water. Residue can remain in scratched, porous surfaces, pressure washing can break corners, and a box may be reloaded before it has dried.
Start with what the box will carry: closed packs, exposed food and non-food loads do not carry the same hygiene risk. Which of them may go into reuse is written by product in the operation's HACCP or hygiene plan.
The wash method is written down too: water temperature, chemical, contact time, mechanical action, rinsing and drying. On every return, check odour, discolouration, cracks, particle loss, softening and lid fit; a box that fails does not go back into usable stock.
If the returnable flow is continuous, compare the total cost with a rigid container designed for washing and tracking; an uncontrolled cycle is not a saving.
