When something you eat makes you sick, your natural impulse is to blame the food and never eat it again. With food allergies, however, you can’t blame everything on the food. After all, most people can enjoy the same foods that make you sick without experiencing even the slightest reaction.

Food allergy is not solely a problem with a particular food. The problem is your body’s response to that food. Some foods clearly are much more prone to inducing allergies than others, but the real problem is with the body’s reaction to these foods.

The stuff in some foods that trigger reactions in some people are proteins — molecules constructed out of building blocks called amino acids. As you know, proteins are essential in building muscle and repairing cells; they also play an important role as hormones, enzymes, and antibodies.

Every protein has a unique, genetically mapped structure. You probably couldn’t discern one protein from another in a police lineup, but your immune system has an eagle eye for identifying proteins. Within seconds after a specific protein enters your system, your immune system identifies it as friend or foe.

When your immune system mistakenly identifies a food protein as an enemy invader, it jumps into attack mode and causes all the symptoms that make you miserable — hives, rash, nausea, breathing difficulties, and so on. What is it about a particular protein that makes it problematic?

Researchers continue to study that question, but most suspect that problematic proteins are high-profile molecules that the immune system can easily spot. Problematic proteins commonly exhibit the following traits:

• Unique shape or folding pattern: Peanut proteins, for example, are folded with the protein pieces that are responsible for stimulating the immune system exposed rather than concealed inside the molecule.

• Size: Protein molecules that trigger allergic reactions tend to be rather large . . . comparatively speaking, of course.

• Stability: Allergenic proteins may be more stable, requiring additional time for your system to break them down into innocuous amino acids.

Nature abhors a vacuum, and so does the human mind. When people are unaware of the protein-immune-system connection, they concoct all sorts of theories about what actually causes food allergies. Some of these theories are valid to certain point, others rarely apply, and a few are just plain bunk.

Can genetically engineered foods trigger allergies? They sure can, although the occurrences are rare. To genetically engineer a food, scientists introduce genetic material from one food into another. If they mistakenly introduce an allergenic protein from one food into another, the receiving food also contains the allergenic protein, which can also trigger a reaction.

Histamines

During an allergic reaction, your immune system produces histamines that trigger symptoms, so it stands to reason that consuming histamines would trigger similar symptoms, and consuming histamines sometimes does just that. Several foods contain histamine or histamine-like substances of their own:

• Scombroid fish: The Scombridae family of fish, including tunas and mackerels and their close cousins, bluefish and mahi-mahi, contain a toxic histamine generated by bacterial degradation of substances in the muscle protein. This natural spoilage process is thought to release additional by-products that intensify the toxic effect and can cause scombroid poisoning.

• Strawberries: People who have “allergic reactions” to strawberries are often simply more sensitive to the histamines they contain.

• Tomatoes: When tomatoes produce symptoms similar to those of an allergic reaction, histamines may be to blame.

• Chocolate: A food allergy to chocolate is rare, but chocolate may contain higher levels of histamines that can trigger allergic-like symptoms.

• Wine and beer: Some wines and beers contain elevated levels of histamines. Wine producers have picked up on this and some now offer histamine-low or histamine-free wine. Red wines typically contain more histamines than white wines.

The levels of histamine present in these foods are usually not capable of causing reactions but they can and occasionally do cause allergic-like reactions. Scombroid poisoning can cause severe reactions, but reactions to other foods that contain elevated histamine levels are typically mild, if they even occur.

Food Additives

Most processed foods contain additives including dyes, preservatives, and a variety of other chemicals to make foods more stable, prettier, or tastier. If you experience reactions consuming foods that contain a particular additive, the food itself is not at fault, and you’re not really experiencing a true food allergy.

You’re allergic to the stuff in or on the food. Here are the two most common culprits:

• Sulfites: Sulfites can cause severe reactions in people who are sensitive to them. Asthma sufferers generally face a higher risk. Food manufacturers often add sulfite to wines, some baked goods, and even on fruits and vegetables to keep them fresh. Strict labeling laws are in place for sulfites, because even low levels can cause severe reactions in some people.

• MSG (monosodium glutamate): MSG is another food additive that occasionally causes adverse reactions. Because Chinese foods commonly contain high levels of MSG, reactions it causes are often referred to as “the Chinese restaurant syndrome.” Headache and flushing are the most common symptoms, but sweating, increased heart rate, and anxiety can also occur.

Reactions to other food additives are relatively uncommon. They do occur, especially to food dyes, but a history of such a reaction is usually not borne out by a full evaluation.

Many people believe that they have reacted to a dye or preservative, but on closer inspection allergists find that the patient is actually eating the same substance in high concentrations in many other foods without experiencing any reaction. Allergists have no allergy tests for most of these dyes and preservatives. Health history and challenge testing are the best diagnostic tools currently available.

Manufactured-Chemical

Chemical engineers have designed a wide variety of products to improve our lives — everything from pain relievers to zero-calorie artificial sweeteners. But some bodies haven’t evolved to assimilate this stuff. Any of hundreds of manufactured chemicals can trigger allergic-like reactions, but one of the most common classes that cause problems are NSAIDs (Nonsteroidal Anti-Inflammatory Drugs).

Pain relievers including aspirin, Motrin, Advil, and Alleve are known as NSAIDs. These pain relievers are great for treating headaches and pain in most people, but they can cause severe reactions in some. Manufactured chemicals can’t be considered foods, so reactions to them are not considered the result of food allergies. The medical community attributes reactions to these substances to chemical sensitivities.

Food Intolerances

When a food makes you sick, you may be inclined to blame it on a food allergy, but foods can make you ill for other reasons — the most common of which is that you have an intolerance of the food. With a food intolerance, symptoms occur because your body has trouble digesting or breaking down the problem food.

The classic example of a food intolerance is lactose intolerance, in which people experience nausea, vomiting, abdominal pain, or diarrhea because they’re unable to break down the milk sugar called lactose. Lactose intolerance is completely different from milk allergy in which the immune system has developed a sensitivity to milk protein.

Nature’s Poisons

If you try to eat a lion, the lion fights back. Although inanimate edibles can’t claw your eyes out, they often contain toxins that protect them from predators or simply exist as part of the plant’s chemistry. Almonds, for example, contain cyanide. Fruits commonly have a laxative effect on animals, to enable any seeds that an animal swallows to quickly move through their digestive track, so the seeds are not damaged.

Other foods contain chemicals to ward off bacteria and fungus infection. Some toxins in foods can be quite deadly. Mushroom hunters, for example, have to be able to tell a poisonous mushroom from one that’s harmless, because some mushrooms can be deadly.

Several varieties of fish also produce their own toxins. One of the most well known is the puffer fish, which can contain a potent toxin. Natural toxins in foods can make you ill, but your illness from those toxins has nothing to do with food allergies.