Mustard sauces are typically made with mustard seeds, vinegar, wine (for Dijon mustard), spices, and other ingredients. These ingredients are naturally gluten-free. But, this is not enough to guarantee that mustard is always gluten-free. When it is produced in a facility that also produces other products containing gluten, cross-contamination is possible. Thus, always check the allergen information on the label or reach out to the manufacturer for further details.