Adverse reactions that are often confused with food allergies

Shirley Yeung, HK BioTek Nutritionist

Food can cause different types of effects on the human body. However, adverse reactions are not necessarily food allergies or sensitivities. Sometimes the symptoms are similar so it is often confused. Although there are many similarities in these reactions, there are still differences between them. The most obvious one is that they do not involve the immune system.

A. Food intolerance

i. Lack of digestive enzymes

The occurrence of food intolerance is mainly due to the lack of certain digestive enzymes in the intestines, inability to break down specific substances in some foods, or direct stimulation of certain substances in food. The biggest difference between this problem and food allergy or sensitivity is that the response does not involve the immune system. The most common example of food intolerance is "lactose intolerance". This is one of the major reasons why some people will often have diarrhoea after drinking milk. Lactose is the main sugar in milk, and lactose need to be broken down by lactase to make it into more digestible galactose and glucose, which will be easily absorbed by the body.

Asians generally lack lactase. Without this enzyme, they cannot break down and absorb lactose in milk. Therefore, we may feel uncomfortable in the stomach and even have symptoms such as bloating, fart, stomach pain or diarrhoea. In addition to lactose, alcohol intolerance is equally common among Asians. Some people will have symptoms like blush, rash, heart palpitations and headaches after drinking because there are relatively few enzymes that break down alcohol in the body.

ii. Allergic-like inflammation

Some people occasionally have an allergic reaction after eating seafood, rash will appear or even they have difficulty in breathing. However, the symptoms do not appear every time they eat seafood. Actually, some ingredients in the food, such as histamine, serotonin, and tyramine can cause an allergic-like reaction. For example, some people who have eaten seafood will have itchy body, rash, and even swollen face, but he may not be allergic to certain seafood. Probably it is due to the unfresh seafood start to rot and produce too much histamine. When we eat these unfresh seafood, we will have a series of allergic-like reactions. Besides, both cheese and beer contain tyramine and histamine, excessive intake also has the potential to cause headaches, runny nose and other problems. This phenomenon is called pharmacological food intolerance.

iii. Food additive

An adverse reaction to a food addictive is also defined as food intolerance. Many processed foods use food additives such as flavor enhancers, preservatives, sweeteners, and pigments to enhance the taste of food and extend the shelf life. Common additives are MSG (E621) used as a flavor enhancer, sodium benzoate (E211) used as a preservative, lemon yellow (Tartrazine, E102) used as a pigment, and artificial sweetener aspartame (Aspartame, E951). An addictive in a restaurant may provoke a myriad of symptoms in some people, including rash and headache but not due to food sensitivity or food allergy.

B. Food Poisoning

Food poisoning is usually caused by contaminated food. Food can be contaminated with bacteria, viruses, parasites or chemical toxins. Common symptoms include abdominal pain, diarrhoea, and vomiting. If not treated properly, the patient may have serious complications or even death. In 2015, the World Health Organization estimates that approximately one in 10 people in the world have experienced discomfort due to eating unclean food each year, and 420,000 people have died of food poisoning. One of the common bacteria causing food poisoning is Salmonella, which often occurs in uncooked meat, egg products, or unpasteurized milk. Another common bacterium, Staphylococcus aureus, has the opportunity to appear in foods that do not require reheating, such as sandwiches. In the 2018 Winter Olympics held in PyeongChang in South Korea, several staff members have food poisoning symptoms such as vomiting and diarrhoea after eating food infected by Innovirus.

C. Psychosomatic Food Aversion

Most of the adverse reactions caused by psychological factors are due to past unpleasant eating experiences or dislike of the food, which leads to resistance to food and causes a series of uncomfortable reactions. This reaction is purely a psychological factor and is easily overlooked in treatment. For example, some people believe that they are allergic to pork. Every time they eat pork, they will have various uncomfortable symptoms. However, there will be no such reactions if they eat pork without knowing it.