Of the plant aromatics, we can say with certainty that food chemical intolerant individuals react to the following chemicals:

• Salicylates
• Natural benzoates
• Natural gallates

However, food chemical intolerant individuals seem to react to a diverse range of plant derived aromatic chemicals, not merely to salicylates. This is called cross-reactivity and occurs when chemicals are similar enough in structure that they fire the same receptors in the body. What this range of chemicals have in common is that they exhibit the ability to interfere with arachidonic acid metabolism and prostaglandin production, and a tendency to increase inflammatory leukotriene production through the inhibition of cyclooxygenase (COX) I/II and/or the induction of lipoxygenase (LOX). Many of these chemicals also suppress the production of inducible nitric oxide synthase (iNOS). The group includes relatively strong COX II inhibitors like salicylates, and also weaker COX I/II inhibitors from a broad range of polyphenols and flavonoids. Even some vegetable carotenoids are weak COX II inhibitors that may affect those with extreme sensitivities (however the vitamin A found in animal foods in the form of all-trans retinoic acid actually induces COX II enzymes). While salicylates act as selective COX II inhibitors, some polyphenols also inhibit COX I, an enzyme whose activity is required by the whole digestive system for normal function and protection. Other polyphenols simultaneously suppress COX I/II and LOX production. Though LOX induction is problematic and leukotrienes are involved in a number of food chemical intolerance syndromes such as asthma and eczema, COX inhibition in and of itself appears to be problematic too, as prostaglandins are responsible for regulating autonomic neurotransmitters and interact with dopamine in the brain.

Polyphenols that intolerant individuals might react to include the following COX inhibitors (not an exhaustive list):

• Anthocyanidins
  • Cyanidin (cherries, berries)
  • Proanthocyanidins (chocolate, broad beans, nuts, wine)
  • Delphinidin (berries, wine)
• Flavinoids
  • Hesperetin (citrus fruits, peppermint)
  • Naringenin (citrus fruits)
  • Apigenin (parsley, peppermint, thyme, salad vegetables)
  • Luteolin (thyme, parsley, peppermint, peppers, rosemary, citrus, leafy green vegetables)
  • Isorhamnetin (parsley, dill, chives, onions) Kaempferol (capers, dill, kale)
  • Myricetin (parsley, berries, broadbeans, tea, citrus)
  • Quercetin (capers, dill, buckwheat, cocoa, onions, peppers, berries)
  • Rutin (grapes, buckwheat)
• Gallates and catechins
  • Catechin (broadbeans, fruits)
  • Epigallocatechin (broadbeans, tea)
  • Epicatechin (broadbeans, fruit, tea, wine)
  • Theaflavin (tea, buckwheat)
  • Gallates (tea)
• Other polyphenols
  • Curcumin (turmeric)
  • Tannins (tea, coffee, wine, fruits, wild rice)
• Carotinoids
  • Beta and alpha carotene
  • Lutein/zeaxanthin
• Glycoalkaloids (nightshades e.g. potatoes, tomatoes, eggplant, capsicum, tobacco)
  • Solanine
  • Chaconine

Free glutamates form when protein is degraded by lengthy cooking or the action of autolytic or bacterial enzymes. Protein is broken down into its constituent parts – amino acids – one of which is glutamate. Amines form when amino acids are broken down even further (decarboxylated) by autolytic or bacterial enzymes. Amines should not be confused with amino acids or proteins, as these are largely safe. Free glutamates and amines are neurotransmitters. Innate capacities to neutralise dietary neurotransmitters vary widely between individuals. Multiple hormonal and genetic factors can leave some people with a very low tolerance. Dietary neurotransmitters act directly to disrupt the normal neurotransmitter balance of the body and brain. Food chemical intolerant individuals can experience reactions to the following dietary chemicals:

• Amines
  • Histamine
  • Serotonin
  • Dopamine
  • Norepinephrine (noradrenaline)
  • Epinephrine (adrenaline)
  • Phenylethylamine
  • Tyramine (a pseudo neurotransmitter that acts on adrenaline receptors)
  • Tryptamine
  • Putrescine
  • Cadaverine
• Free amino acids
  • Free glutamates (MSG)
  • N-methyl-D-aspartic acid (NMDA) and/or aspartate
  • Glycine (potentially, under some interactions)

Some food chemical intolerant individuals are particularly sensitive to sulphur or sulphites found naturally in some foods, particularly in vegetables. This may be due to the ability of sulphides and sulphites to induce histamine degranulation. Sulphites are notorious for causing breathing problems. Foods include cabbage-family vegetables, asparagus, onion and garlic, and possibly also eggs in some sensitive individuals. Sulphur compounds include:

• A variety of natural thiol compounds including methanethiol
• A variety of natural sulphide compounds including Dimethylsulphide (DMS)
• Natural sulphites
• Glucosamine sulphate, chondroitin sulphate, magnesium sulphate AKA epsom salts (break down into sulphites in the body)

Some food chemical intolerant individuals may be particularly sensitive to nitrates and nitrites found naturally in some foods. Nitrates and nitrites are added to meats like ham and bacon to preserve them, but high amounts are also found in some vegetables like spinach and beetroot,  and in particular, celery. Amounts will vary in vegetables depending on how they have been grown. Nitrates and nitrites are notorious for causing headaches and delayed muscle tension reactions the day after consumption, possibly due to their interaction with the body’s production of nitric oxide. Sometimes bacon marketed as “natural” will contain celery extracts as a substitute for nitrates – and will cause the same symptoms as nitrates in sensitive individuals.

A significant proportion of (but not all) food chemical intolerant individuals also have problems with gluten grains and cow’s dairy products, and these intolerances often occur together. The common factor appears to be the opioid-like peptides produced when proteins from these foods are broken down during digestion. Opioid-like peptides act on the body’s endogenous opioid receptors, having diverse effects including altering pain perception, respiration, GI motility and sociability. Opioid-like peptides are found in the following proteins:

• Casomorphin (A1 cow’s milk)
• Gluten exorphin (gluten)
• Gliadorphin/gluteomorphin (gluten)
• Rubiscolin (spinach)

Individuals with an opioid-peptide sensitivity who do not tolerate cow’s milk should find that they tolerate goat’s milk without problems. Alternately, failsafers may have genuine food allergies, which can have diverse effects on individuals and many crossover symptoms with food intolerance, including asthma, rashes, and loss of concentration.