The recall, announced on the Food and Drug Administration's website on Monday, affects 890 boxes of its Soylent Powder 1.8 that was shipped to 610 customers.
Soylent says it issued a recall because the boxes "may contain undeclared milk." Soylent's 1.8 powder is advertised as dairy-free.
"People who have an allergy or severe sensitivity to milk run the risk of serious or life-threatening allergic reaction if they consume these products," Soylent said in a statement.
Soylent says that the recall is due to a "temporary breakdown" in its third-party manufacturer's production and packaging processes. Soylent says its manufacturer's milk-containing production lines were adjacent to the dairy-free Soylent 1.8 powder production line and there was "potential cross-contact."