Some people are not allergic to food per se, but to the additives we put during cooking, or processing food items, such as preservatives, food colours and flavor enhancers.

Although allergic reactions to food additives are quite rare (0.12 to 2% of the population), for some sensitive people, they can cause serious effects. Among the most common food additives that trigger allergic reactions are:

Sulphites: sulphur dioxide, sodium sulphite and potassium metabisulphite
Benzoates: sodium benzoate, benzoic acid and methyl-paraben
Nitrates
Monosodium glutamate (MSG)
Tartrazine

Here's an article from Health24 that summarizes the role of these additives in food, and the symptoms that show in people overly sensitive to these compounds.

Particularly interesting is portion about MSG sensitivity or allergy, also termed as "Chinese restaurant Syndrome" because the Chinese cuisine is notorious for using a lot of this substance.

The jury is still out about the actual role of MSG in Chinese Restaurant Syndrome because anyone eating at a Chinese restaurant could ingest a wide variety of potential allergens, such as fish, peanuts, soya and other beans, nuts etc. The present finding is that a sensitive individual who eats a large amount of glutamate in the form of MSG and soy sauce on an empty stomach may develop Chinese Restaurant Syndrome symptoms.

If you have true glutamate sensitivity, you should also be showing symptoms when eating other food items such as some types of cheese, poultry and other vegetables which contain natural glutamate.

Lastly, here's the final advice from Dr. Ingrid van Heerden:

If you have been diagnosed with an additive sensitivity or allergy, it is important for you to read food labels carefully and avoid processed food that contains the specific additive that you are allergic to. The only exceptions are MSG or glutamate allergy where patients must also avoid foods that contain natural glutamate as listed above, and benzoate allergy patients who need to cut out cinnamon, tea and berry fruits.

Click here to read the full article.