You’ve been diagnosed with celiac disease or another gluten-related disorder. You know you have to avoid wheat, rye, barley and ingredients and products derived from them. But are you aware of the dangers of cross-contact?
Before you begin your own gluten-free adventures at home, or decide to try eating out, you’ll need to be aware of all of the places in a kitchen where gluten may lurk. It doesn’t take very much gluten to make you sick! Even just a crumb of gluten is enough to start the autoimmune response in people with celiac disease, even if symptoms are not present. Many people find cross-contact to be one of the most difficult parts of the gluten-free diet to manage.
Frequently Asked Questions about Cross-Contact
What is cross-contact?
Cross-contact is when a gluten-free food or food product is exposed to a gluten-containing ingredient or food – making it unsafe for people with celiac disease to eat. There are many obvious (and not-so-obvious) sources of cross-contact at home and in restaurants and other foodservice locations. There is even a risk of cross-contact before ingredients make it to the kitchen, such as during the growing, processing, and manufacturing processes.
While it may seem like a challenge to remember and be proactive about all of the possible sources of cross-contact at first, your improved health will make the effort worth it. Read on to better understand some of these sources and what you can do to prevent cross-contact.
What is cross-contamination?
Cross-contamination is a term that implies that a food has been exposed to bacteria or a microrganism, which could result in a foodborne illness like salmonella. By definition, it can lead foodservice and other industry professionals to believe that if a food is “contaminated” by gluten, they can simply “kill off” the contaminant. However, gluten is a protein (not a type of bacteria) and proteins cannot be “killed off” using heat or disinfecting agents like most bacteria can be.
The term "cross-contact" more accurately reflects that a gluten-containing food cannot come into contact with a gluten-free food. If we speak the same language as chefs and foodservice professionals, we are more likely to have a better experience when dining away from home.
What are hidden sources of gluten?
Gluten can hide in lots of places, even in your home. Some people opt to maintain an entirely gluten-free household, but for many, that's not possible, especially because cabinet space and budget concerns can play into the decision.
Download: Infographic: Hot Spots at Home
Can I use the same toaster for gluten-free and gluten-containing items?
The short answer: No, you cannot use the same toaster for both gluten-free and gluten-containing items.
An explanation: Celiac disease experts strongly recommend that you buy a separate toaster for gluten-free items to avoid cross-contact with gluten-containing foods. However, there are reusable “toaster bags” on the market which can be used in a pinch to prevent cross-contact. These can be useful for travel and eating at a friend or relative’s house. Toaster bags are not foolproof, and caution must be used to ensure that crumbs from gluten-containing items do not fall into the bag. It is also important to remember to never place the bag itself on gluten-free plates of food, as the outside of the bags will expose the other foods to any gluten it came into contact with in the toaster. Similar caution should be used when preparing gluten-free foods in toaster or convection ovens.
Can I prepare gluten-free foods in toaster or convection ovens that have been used to make gluten-containing food?
The short answer: There is a high risk for cross-contact.
An explanation: Convection ovens use a fan to circulate air around food. This process can cause cross-contact because gluten particles can be blown by the fan. You can still use a convection oven that has been used to prepare gluten-containing foods, but only as long as you keep gluten-free foods tightly covered when cooking. Toaster ovens are acceptable to use too, and using foil or a clean tray on the rack helps create a barrier from any crumbs. Also, be sure to thoroughly clean the oven in between uses, even if there are no visible crumbs.
Can I use the same sponges and dish rags to clean gluten-free cookware as I use for cookware that has been used to make gluten-containing items?
The short answer: No, you should have separate sponges and dishrags to clean gluten-free cookware. Paper towels may not be “green” but you can clean up and toss the gluten-containing crumbs.
An explanation: Gluten cannot be sanitized away, so any gluten that remains on sponges or dishrags can be transferred to otherwise clean plates. Make sure to also use fresh dish water if you hand wash your dishes, as particles of gluten in the water can also be transferred to otherwise clean dishes when rinsing. Save dishes that held gluten-containing foods for last when hand-washing dishes.
While gluten cannot be “killed off,” dishes must still be washed thoroughly to eliminate any remaining particles on them. Dish soap combined with warm water accomplishes this much more effectively than simply running dishes under water. Beyond Celiac Scientific/Medical Advisory Council member Rachel Begun, MS, RDN, highlights these steps for cleaning dishes in shared kitchens:
- Dry wipe to remove all crumbs and bits and pieces of food residue before cleaning
- Wash thoroughly with warm, soapy water
- Where possible, clean by running through the dish washer. Or, use a home sanitizing solution for necessary equipment.
- Either let air dry or wipe with a clean towel that hasn’t come into contact with gluten
Can I use condiments from the same containers that have been used to prepare gluten-containing foods?
The short answer: No!
An explanation: Utensils that are used to spread butter, peanut butter, jelly, mayonnaise, cream cheese and other condiments will expose the product to gluten which can then be spread onto your gluten-free breads, bagels, etc. As a solution, you may find condiments in squirt bottles useful as long as those using the condiments are well aware that they cannot wipe the tip of the squirt bottle on their gluten-containing foods. It is safest to have separate condiments, and to clearly label the condiments that are dedicated gluten-free.
Families (or roommates) may find it helpful to discuss gluten-free kitchen dos and don'ts and should express the importance of confessing mistakes. If someone accidentally dips his or her knife in the gluten-free jar, it is his or her responsibility to make sure family members or roommates are well aware. A similar situation can happen with dips. If someone dunks a gluten-containing pretzel into the vegetable dip, it is no longer safe for someone with celiac disease to consume.
Can I use the same water for boiling gluten-free pasta, steaming vegetables, and thickening gluten-free sauces that was used to boil gluten-containing pasta?
The short answer: No, you must use clean water.
An explanation: This remains a very common misconception when the term “cross-contamination” is used. Some believe that boiling water after making gluten-containing pasta or other gluten-containing foods will “sanitize” the water, and make it safe to prepare gluten-free foods. Gluten cannot be “killed off” or “disinfected,” so it is not safe to use the same water to make gluten-free foods that was also used to make gluten-containing foods. This is a practice called comingling. This should also be kept in mind when using colanders to strain pasta. Gluten-free pasta should always be strained in a clean, preferably dedicated, colander.
Can I use the same oil for frying gluten-free items that was used to make gluten-containing fried foods?
The short answer: No, a separate fryer must be used for gluten-free items to avoid cross-contact.
An explanation: Similar to the misconception about using the same water to boil both gluten-containing foods and gluten-free foods, it is also not safe to use the same oil to fry these items. High heat will not eliminate gluten in the oil, so fryers used to make breaded or battered items would not be safe to use for gluten-free French fries, corn tortilla chips or other gluten-free items.
Are cutting boards a source of cross-contact?
The short answer: Yes, cutting boards can be a hot spot for sources of gluten.
An explanation: Knives can cause cuts on the surface of cutting boards, and these are hard to clean out completely. If a cutting board is used to slice, cut or dice gluten-containing items – like bread or dough – gluten can get stuck in these crevices and transfer the gluten to your food. Make sure to purchase a cutting board that is only used to cut gluten-free foods. Color-coding is an effective way to differentiate between the gluten-free cutting board and the cutting board that can be used for gluten-containing items.
Can I safely prepare gluten-free foods on the same grill or griddle that was used to prepare gluten-containing foods?
The short answer: No, it is not recommended that you use the same grill or griddle to prepare gluten-free foods that is used to make gluten-containing foods.
An explanation: Crumbs from toasting hamburger buns or sticky marinade residue can easily be left on the grate of the grill, and it is difficult to properly clean after it has charred on. Also, it's common for restaurants and other foodservice establishments to cook both naturally gluten-free foods like omelettes and breakfast potatoes and gluten-containing foods like pancakes and French toast on the same surface such as a griddle or flat grill. We recommend that you ask questions and assess your risk for cross-contact. If the char grill never sees bread – and many restaurant grills do not – and only raw meats and vegetables with no marinades are used, a char grill is a safe choice. Assess your risk by asking the chef or manager if they toast bread products on the grill. Also ask if the grill or griddle is used to cook marinated foods and gluten-conataining foods like pancakes. If the grill has been exposed to gluten, heavy, sturdy foil can be put on the grill or a sauté pan should be used instead. If there is a great risk of gluten exposure at home, you may choose to purchase a small grill that can be dedicated to only preparing gluten-free foods.
Can I make gluten-free waffles using the same waffle iron that was used to make gluten-containing waffles?
The short answer: It is not safe to use a waffle iron to prepare both gluten-containing and gluten-free waffles.
An explanation: Waffle irons are incredibly difficult to clean thoroughly, and residual gluten may be left on the iron even after cleaning. You should buy separate waffle irons (and other similar appliances) to prepare gluten-containing and gluten-free waffles to avoid any chances for cross-contact.
Can the refrigerator door handle really expose me to gluten?
The short answer: Yes! All handles in the kitchen can expose you to gluten.
An explanation: Although not the most common source of gluten, the refrigerator door handle can contain sticky gluten residue. For example, a chef is preparing cookies or has flour-dusted hands and suddenly realizes they're missing an important ingredient. They then may hastily wipe them on the dish towel or apron (which are now also sources of unwanted gluten!) and open the fridge. Any residual gluten that was on their hands is now on the refrigerator door handle and may be a source of cross-contact later on. If you do not have a dedicated gluten-free kitchen at home, make sure to regularly clean your refrigerator door and other handles in the kitchen to ensure that you will not accidentally be exposed to gluten when you’re grabbing a quick bite to eat from the fridge!
Should I store my gluten-free items on the bottom or top shelf of my pantry and refrigerator?
The short answer: Store your gluten-free items on the top shelf in a dedicated area.
An explanation: We recommend that you keep gluten-free items on the top shelf of your pantry, refrigerator and freezer to prevent crumbs of gluten-containing items from falling into gluten-free foods. Make sure to also have a dedicated gluten-free shelf of foods, as it can be easy to mistakenly grab the gluten-containing bread crumbs because they were right next to the gluten-free ones. Label your gluten-free foods with colored tape or stickers to ensure that the whole family can recognize their status confidently.
Do I need to worry about airborne flour?
The short answer: Yes.
An Explanation: Most people will be surprised to know that flour can stay airborne for 12-24 hours depending on ventilation and quantity of flour. If there is a risk of any flour or particles of gluten in the air, it is safest to avoid those areas for the next 24 hours. While simply touching gluten will not harm an individual with celiac disease, there can be a risk of ingesting airborne gluten, which is usually caused by flour. It is also important to remember not to prepare gluten-free foods in spaces where there is a risk of airborne gluten, as particles will settle on the food, making it unsafe for those with celiac disease to eat. Some of the most common places where this type of cross-contact can occur include pizzerias and bakeries.
Can I safely eat at a buffet that has both gluten-free and gluten-filled foods?
The short answer: Sometimes.
An explanation: While there may be gluten-free options on a buffet, there is no guarantee that they have not come into contact with gluten. Even when those making the food claim to be very aware of their preparation methods, other people eating at the buffet may not be. Spoons may be set back in the wrong dish, and tongs may be used to pick up several different foods before being put back in the right spot. Gluten-filled foods could spill into the gluten-free foods. Thermometers that are used to check if food is safe to consume may be used in gluten-filled and gluten-free foods without proper cleaning between checks. These are just a few examples of the potential for cross-contact in buffets. As a solution, you can ask to speak to the chef to see if they can bring out a freshly made plate of gluten-free foods directly from the kitchen. Or, you can work with the chef and catering company to make sure that you are able to serve yourself first, before cross-contact can occur.
Should I be concerned about cross-contact during the growing and manufacturing processes?
The short answer: Yes, absolutely!
An explanation: It is important to know how your food is made, from farm to table, in order to avoid possible gluten exposure. To voluntarily label a product gluten-free in the U.S., it must contain less than 20 ppm gluten, as mandated by the FDA. However, if a product is NOT labeled gluten-free, but you do not see any gluten-containing ingredients listed, this does not mean that it is under the same 20 ppm threshold. This is because manufacturers are manufacturers are not required to call out “gluten” in food products; the FDA gluten-free labeling rule is voluntary for food manufacturers. To determine whether there was a risk of cross-contact during the growing and/or manufacturing processes, it is best to call the manufacturer and inquire whether they batch test their product for gluten, if they know how their raw materials were sourced and produced, and what procedures they go through to prevent cross-contact in the factory.