food ALlergies and intolerances

More and more often these days we hear about people with allergies and intolerances. Although they are similar, a food intolerance and an allergy are actually two different things. An allergy is far less common, with only 2% of adults and 8% of children having one.

What is an allergy?

An allergy is an immune response, triggering an IgE antibody release, to a protein in a food or environmental substance that the body mistakenly sees as a threat. An allergy triggers a sudden and severe inflammatory response. It is often referred to as atopy (a genetic tendency to allergic hypersensitivity of environmental proteins to parts of the body not directly in contact with the allergen). The IgE antibodies create an extreme inflammatory response and the activation of white blood cells known as mast cells and basophils.

Some people can be severely allergic to environmental substances (airborne particles like dust and pollen), foods (such as fish, shellfish, nuts, milk and eggs) or medication (aspirin, penicillin and antibiotics).

Insect stings, antibiotics and certain medications can affect several organs, such as the digestive, respiratory and circulatory systems, this is known as anaphylaxis (a systemic allergic response). Depending on the individuals susceptibility this can lead to oedema, hypertension, bronchoconstriction, coma and even death. Less severe, yet still serious allergic reactions, include eczema, hives, hay fever and asthma. Rashes, wheezing, a runny nose and itching are all classic allergy symptoms too.

Allergens that are inhaled - such as dust and pollen, will lead to asthmatic symptoms, narrowing of the airways (bronchoconstriction), wheezing, coughing, shortness of breath and a production of mucus in the lungs. In these cases the allergens generally affect areas that are in direct contact with the air, so the nose, eyes and lungs.

Allergens that are ingested - such as medication and food, will cause symptoms such as diarrhoea, abdominal pain, vomiting, bloating and itchy skin.

It is possible to analyse your blood for allergen specific IgE, and also test the skin to see the response to known allergens. Treatments include anti-histamines, steroids, immunotherapy, desensitises and of course allergen avoidance, for extreme reactions an adrenalin injection may be required.  

Signs and symptoms

Nose - swelling of nasal mucosa (rhinitis).

Sinuses - allergic sinusitis.

Eyes - itching of the conjunctiva, redness (conjunctivitis).

Airways - coughing, wheezing, dyspnea (shortage of breath), sneezing and bronchoconstriction, asthma, angioedema (swelling of the airways).

Ears - feeling blocked, pain and impaired hearing (lack of Eustachian tube drainage).

Skin - rashes, eczema, hives.

Gastrointestinal tract - vomiting diarrhoea, abdominal pain and bloating

More obscure allergens

Some chemicals that appear naturally in foods can trigger allergic reactions in some people. These naturally occurring chemicals often add flavour and smell to a particular food. An allergy test may be necessary to detect these more obscure chemicals.

Monosodium glutamate (MSG) - isolated from seaweed by a Japanese chemist, also occurs naturally in camembert, parmesan, tomatoes, soy sauce and mushrooms. MSG stimulates nerve endings.

Vasoactive amines (tyramine, serotonin and histamine) - these are known for causing migraines in susceptible people. These chemicals can be found in pineapples, bananas, vegetables, baked meat, wine, chocolate, citrus fruit, avocado and mature cheese. Amines have a dilating effect on blood vassals creating an increase in blood flow which would explain the migraines and nasal congestion in some people. 

Salicylates - these are aspirin like compounds found in a wide variety of herbs, spices, fruit and vegetables. It is possible to have allergies to these and they can cause hives by acting directly on mast cells and can also worsen a hive reaction.

What is a food intolerance?

A food intolerance or sensitivity produces an IgG antibody reaction. Unlike an allergic reaction, symptoms are slow to manifest, taking between one and thirty-six hours. Food intolerances can be tricky to identify as they don't show on allergy testing.

Typical symptoms include gastrointestinal problems such as bloating, diarrhoea, nausea, vomiting, irritable bowel, skin rashes, fatigue, joint pains, dark circles under the eyes or night sweats. Substances inside certain foods can aggravate an existing condition, but don’t necessarily cause the problem. 

There are a few conditions associated with a food intolerance such as eczema, hives, recurrent mouth ulcers, migraines and headaches. Hyperactivity in children and chronic nasal congestion are less common but worth investigating as possible food intolerance. 

The following are all examples of common food intolerances:

  • Wheat
  • Gluten (a sensitivity to gluten is different to coeliac disease)
  • Dairy products, including cheese, milk and yoghurt
  • Food additives, such as sulphates and dyes
  • Strawberries, citrus fruits and tomatoes
  • Chocolate
  • Eggs

What is lactose intolerance?

Lactose intolerance should not be confused as a cow’s milk allergy. As previously mentioned, an allergy and intolerance have a different immune response. It is possible, generally in children under 3 years old to have a dairy allergy, to one or both of the milk proteins (casein and whey). A dairy intolerance is actually an intolerance to lactose, the sugar in milk, and an inability to digest lactose. This could be caused by a deficiency in the enzyme lactase needed to metabolise lactose. The lactose should be metabolised and absorbed by the lactose, but it stays in the gut and instead feeds the gut bacteria, which release acids and gasses creating typical symptoms of intolerance. This deficiency is seen a lot in ethnic groups such as Chinese and Hispanic.

Lactose intolerance is rare in infant babies, however congenital lactase deficiency means this person will remain intolerant for life.

Common symptoms are wind, diarrhoea, bloating, stomach aches/rumbling, and feeling sick.

There are a few tests such as a hydrogen test, lactose tolerance test, milk tolerance test or stool test to determine a possible lactose intolerance. However, simply eliminating the dairy for a few weeks should give you an idea if you have an issue. Most people can still digest small amounts of lactose, and there are a lot of lactose free products now on the market.

What if it's not an allergy or intolerance?

It's possible to suffer symptoms similar to those cause by an allergy or intolerance and for there to be a different explanation. For example:

An enzyme deficiency - like that of lactase in a lactose intolerance can be one cause. Alcohol dehydrogenase is an enzyme needed to metabolise the toxic breakdown products of alcohol. When there is a deficiency of this enzyme susceptible people may experience flushing and nausea.

Coeliac disease - is a common digestive condition where a person has an adverse reaction to gluten. Interestingly, coeliac disease is not an allergy or intolerance, but an autoimmune condition of the small intestine that appears in genetically predisposed people, where the immune system mistakes a protein found inside gluten (gliadin) as a threat to the body and attacks them.

Gluten is a protein found in wheat, rye and barley that damages the intestine of people with coeliac disease. About 1 in 100 people in the UK have coeliac disease, but it's estimated that around half a million aren't diagnosed.

Symptoms include diarrhea, bloating, diarrhea, chronic constipation, weight loss, pain and discomfort in the digestive tract, anemia and fatigue. Vitamin deficiencies are often noted in people with coeliac disease owing to the reduced ability of the small intestine to properly absorb nutrients from food. Coeliac disease can be accurately diagnosed with a blood test and biopsy

Wheat, barley and rye contain gluten and subsequently gluten is found in many foods that contains these grains like, pasta, cakes, breakfast cereals, most types of bread, certain sauces, some ready meals and most beers are made from barley.

Food aversion - is when someone actually displays physical symptoms to foods they don’t like when seeing and/or smelling particular foods. This is thought to be triggered by emotions associated with the food rather than the food itself.

This article has
been written by
Terry Fairclough