Does Ketchup and Mayonnaise Contain Gluten? Let’s Read the Labels Together

French fries and chicken nuggets — in most households, this is the unbeatable combo on the kids’ menu. Easy to prepare, guaranteed to please, and once it’s on the table, it keeps everyone happy without much fuss. This duo is almost always joined by ketchup and mayonnaise.

For a family eating gluten-free, though, the real question is: does either of these sauces contain gluten?

Let’s go through the labels together.

Where Does the Gluten Risk in Ketchup Come From?

Check a ketchup label and you’ll typically find: tomatoes, vinegar, sugar, salt, spices, modified starch, and some preservatives.

Of these, tomatoes, sugar, and salt are naturally gluten-free. The risk comes down to two ingredients: vinegar and modified starch.

Vinegar: Usually made from fruits like grapes or apples, in which case it’s gluten-free. But if it’s produced using malt, the resulting vinegar contains gluten.

Modified starch: No problem if it’s derived from corn, potato, tapioca, or rice. But if the starch comes from wheat, the product contains gluten.

Preservatives: This is where things get murkier. Labels rarely give detailed information on whether the preservatives used contain gluten — and many manufacturers don’t even disclose that preservatives are used at all. For this reason, choosing preservative-free products, whenever possible, is the safer bet for gluten-free eating.

What About Mayonnaise?

Mayonnaise labels are a bit more complicated, since we run into quite a few food additives on the ingredient list.

At its core, mayonnaise is made from vegetable oil, vinegar or lemon juice, egg, and salt. But in industrial production, these base ingredients are often supplemented with modified starch, sugar, thickeners, preservatives, flavorings, and colorants.

Looking at this list through a gluten lens: vegetable oil, vinegar, lemon juice (or its concentrate), egg, and salt are all gluten-free. The risk is concentrated in the same two places as before — modified starch and additives. That’s why checking for a “gluten-free” label on the packaging is the safest approach when buying mayonnaise.

Don’t Forget About Cross-Contamination

Even when the ingredient list looks clean, the risk of cross-contamination at the production facility should never be overlooked. If a product is manufactured on the same line as gluten-containing products, unintended gluten contamination can end up in the final product.

This is exactly why a clearly stated “gluten-free” label on the packaging matters so much: it signals that the manufacturer has taken the necessary precautions in both ingredients and the production process. Without a clear statement about cross-contamination, consumers simply have no way of knowing whether a product is truly safe.

In Summary

Ketchup and mayonnaise — the duo we so often associate with fast food and reach for at almost every meal — is worth a closer look when it comes to gluten. Here’s the short version:

• The main risk in both products comes from modified starch and vinegar
• Label information on preservatives is generally insufficient
• Without a “gluten-free” label, some risk always remains
• The possibility of cross-contamination should never be ignored

I’d love to hear your questions, thoughts, and suggestions on gluten-free eating.

Wishing you a healthy and happy life. 🌿