Confusion can arise from the fact that there may be pharmacological effects masquerading as an ‘allergy’. For example, the headache, flushing, racing pulse and giddiness that can come on after too much caffeine is really a drug reaction, not an allergic one. Obviously individual variations in trigger thresholds make this one sometimes hard to observe.
Few people understand the incredible range of pharmacological substances that are to be found in plant substances. Most “green-minded” people think of herbs as kind, nurturing and gentle: wouldn’t hurt anyone, right? But, hey, I like to point out that foxglove, hemlock, opium poppy, marijuana, deadly nightshade and countless plants stuffs are dangerous, even poisonous. “Beware the humble carrot” wrote Richard Mackarness; this innocuous looking vegetable contains a neuro-toxin. Not relevant? I had a patient in the 1980s, a young boy, who had epileptic fits every time he ate carrots or anything from the same food family: parsnip, celery, parsley, dill, fennel, coriander etc.
There is no doubt that in the right hands, plants have healing power, but they can also do great harm. Don’t confuse this type of reaction with a true allergy or even intolerance.
Finally, there is the phenomenon of enzyme deficiency, often called ‘inborn errors of metabolism’. Some people are made ill by their inability to detoxify or metabolize foods, chemicals and drugs. An example is lactase deficiency, which causes people to suffer unpleasant abdominal symptoms when they drink milk. Children with phenylketonuria lack the enzyme phenylalanine hydroxylase and are unable to dispose of phenylalanine, which thus accumulates and causes mental retardation and neurological damage.
But deficiencies are not confined to such named disease conditions. There are thousands of enzymes in our bodies, all working in concert. Many of them are dependent on vitamin and mineral “co-factors” to function properly (for example alcohol dehydrogenase, the enzyme which breaks down alcohol, needs zinc and vitamin B1 to work efficiently). Considering possible variations in inherited endowment of enzymes, complicated by missing nutrient factors, the reader will be readily aware that enzyme deficiency can be a very individual thing.
This subject of innate biological variation is something which confuses the picture with respect to allergy and overload. Doctors will insist on foolishly believing that everyone is the same, we are all “average”. In fact only a tiny percent of the population is “average”, no matter what criterion you are measuring, the vast majority are all over the place, some very far indeed from that average figure (taken to its full absurdity this would be like saying the average height for a man in 5 feet 10 inches, therefore people who are under 5 feet or over 6 feet 4 inches simply don’t exist! Can you imagine tailors being as crazy as doctors are in this regard?).
Good reading: Biochemical Individuality by Roger J. Williams