Published March 17, 2025
Many people think "inactive" ingredients in medicines are harmless. But, in some cases they can cause allergic reactions. Sometimes these “inactive” ingredients are food-based fillers that are used when making the medicine. So, these reactions are often related to food allergies. There are more than 170 foods that can cause allergies. Here are the eight most common food allergens that may be used in medicines:
Inactive ingredients are added to medicines for a number of reasons. They tend to make the medicine more stable and easier to absorb. They may also be used to make the medicine taste better. Since these inactive ingredients may be food-based, they can be a hidden source of an allergic reaction for some people.
The Food Allergen Labeling and Consumer Protection Act of2004 requires food products to list common allergens on the label. However, this rule does not apply to drug products. As a result, inactive ingredients in medicines can sometimes be hidden in the drug’s prescribing information or on the product’s label. And there is no standardized way to list the presence of allergens.
Many people think they have food allergies when they actually have food intolerances or sensitivities. A true food allergy can cause serious or life-threatening symptoms, even with a very small amount of food. For example, if someone has a true food allergy, the symptoms usually begin soon after the food is eaten. They may find it hard to breathe or feel their throat tightening, making it difficult to swallow. Their tongue may swell. They may faint or go into shock.
This is different from food intolerance, which usually causes less serious gastrointestinal issues like pain, diarrhea, gas, bloating, nausea, and upset stomach.
Although not a true allergy, celiac disease is an autoimmune condition where gluten, a protein found in wheat, rye, and barley, causes a complex inflammatory reaction. People with celiac disease can get very sick after eating bread, pasta, or crackers that contain these proteins.
Some patients experience symptoms after ingesting a food that is not related to an allergy, intolerance, or celiac disease. This may be due to a food sensitivity, where the body’s immune system reacts, causing various symptoms such as tiredness, skin rashes, confusion, difficulty concentrating, and joint and/or stomach pain. These symptoms are not life-threatening but can be upsetting. Gluten is one of the best-known triggers of food sensitivities.
Avoiding foods that cause a true allergy or reaction is key. However, some people may also avoid certain foods because of religious or cultural preferences.
Here’s what you can do: Any time you go to your doctor's office, pharmacy, or hospital, tell the doctor, nurse, and/or pharmacist about any reactions you have had to medicines and foods. Make sure they know if you have a true food allergy, compared to an intolerance, sensitivity, or preference. They need to document that information accurately in your records. Always check with your doctor or pharmacist about the inactive ingredients in your medicines, especially if you have a true food allergy. This can help prevent unexpected allergic reactions. Before starting any new over-the-counter medicines or herbal supplements, review the label for inactive ingredients. If you are unsure if it contains a food allergen that you may react to, ask your pharmacist before taking it.
