Food Allergy, Pseudoallergy, or Histamine Intolerance?

By Tereza Hubkova, M.D.

Between 1997 and 2007, food allergy diagnoses in the U.S. surged upward 18%. Make no mistake, food allergies can be life-threatening. With any true food allergy, even the smallest amount of the offending food will produce symptoms.

Common symptom include:

• sneezing,
• running nose,
• asthma,
• irregular heart rhythm,
• rash,
• itching,
• facial swelling,
• diarrhea,
• flushing, or
• low blood pressure.

A suspicion of food allergy can be confirmed by skin or blood testing of immunoglobulin E (IgE) levels—when exposed various foods, spices, or preservatives.

When an Allergy Isn't an Allergy

If you have the above symptoms, but your allergy testing comes back negative, you may instead suffer from the lesser know histamine intolerance.

Histamine is a natural substance present in many foods—in varying amounts—as well as naturally contained within your own mast cells (a player in your immune system). Similar to a food allergy, histamine intolerance too can cause headaches, swelling, rash, itching, diarrhea, difficulty breathing, low blood pressure, and in large enough amounts, even shock and cardiovascular arrest.

Healthy people rapidly dismantle dietary histamine by an enzyme called DAO (diamine oxidase). Approximately 1% of us, however, have a hard time metabolizing histamine due to a weakness in their DAO enzyme. This results in a build-up of histamine levels and, hence, the symptoms mimicking an allergic reaction.

Histamine-rich foods include such items as:

• certain fish, 
• ripe cheeses, 
• fermented meats (e.g., salami), 
• alcohol, 
• red wine vinegar, 
• ketchup, and 
• certain vegetables (e.g., spinach and eggplant), 

Moreover, other foods are capable of spurring the release of histamine from your mast cells (e.g., chocolate and nuts), and certain drugs are similarly capable of releasing histamine via the same mechanism: morphine, amitriptyline, and non-steroidal anti-inflammatory drugs (or NSAIDs). Combining histamine rich foods with alcohol, however, is a double whammy—as alcohol not only contains histamine, but it also suppresses our ability to break it down.

Unlike true food allergies, a sensitive person can typically get away with ingesting small amounts of histamine rich foods. It’s the total amount of histamine accumulated that determines whether or not one develops a reaction.

If you suspect histamine intolerance, talk to you physician about testing your histamine levels and DAO activity. At home, you can see if you improve on a low–histamine diet. Sometimes, antihistamine medications like Claritin or Zyrtec may still be necessary.

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