Allergy and Food Intolerance- is there a difference and their link to Bloating and IBS

This is an area that causes a lot of confusion because people often use the two words "Allergy" and "Intolerance" as though they were the same. They are very, very different conditions. The confusion comes because they can have identical symptoms. Let’s go through each in detail.

21.1 Allergy
This means that there is a specific immune reaction being triggered (e.g. asthma attack or itchy eyes if you are allergic to cats, or have hay fever). About 2 people out of every 100 have a food Allergy- so, really not very common at all, unlike IBS, which can affect 20 out of 100 of us.

21.1.1 Allergy and Bloating with IBS
Are the symptoms different between Allergy and Intolerance? Short answer is NO! (as mentioned above. The symptoms that might suggest an Allergy would be tingling or swollen lips, a sore mouth, “hives” (red, itchy skin bumps) or wheeziness. Also, Allergies are more likely to occur in those of us who already have other Allergies e.g. if we have asthma, hay-fever or eczema, we might be more likely to have a food Allergy.

Bloating, Diarrhoea, Nausea, Pain/Discomfort, Lack of Energy etc. can all occur with either an Allergy or an Intolerance. These symptoms just mean the tummy is not happy, but don't tell us why. However, betting our bottom dollar, such symptoms are much more likely to be due to an Intolerance because food Intolerances are so very much more common than food Allergies, which are quite uncommon in adults. So, if you were the betting type, gut symptoms are more likely to be due to an Intolerance than to an Allergy (even if also you do have asthma, eczema etc.).

Food Allergies are far more common in children than in adults and many disappear as we grow, e.g, milk-protein Allergy.

"True" adult Allergies are not very common, occurring in maybe 1 or 2 out of 100 people (IBS affects up to 20 out of 100 of us). Examples of the Allergies that can develop later in life are to: shellfish, kiwi fruit, melons and apples.

Not surprisingly, people who have other non-food Allergies (e.g. hayfever) or related conditions (e.g. asthma or eczema) are more likely to have a food Allergy. But they are still not common.

The reason for these Allergies is “cross-reactivity”. This means that the immune system “sees” similarities between molecules in different foods that are otherwise unrelated. For example, a person with an Allergy to birch tree pollen, may develop an Allergy to apples, cherries and peaches.

21.1.2 Allergy syndromes
There are a lot of odd Allergies that we can rarely get. It is worth mentioning a few of them just in case they ring a bell with you:

• Pollen Food Syndrome: this is where there is cross reactivity between strange bedfellows. In the Northern hemisphere (so, UK, Ireland, USA etc.) there can be a link between having Birch tree "hayfever" and getting an itchy mouth when eating raw (but not cooked) apples (for some people, it can be eating blackberry, raspberry, strawberry, plum, peach, almond, cherry- called "Rosaceae" allergy). In the Southern hemisphere (so New Zealand, Australia etc.) the more common combo is grass pollen and an itchy mouth with raw tropical fruits or watermelon.

• Excercize-induced rash: excercizing after eating wheat, celery or shell-fish can cause a rash or even a severe life-threatening allergic reaction. This is due to the release of the chemical histamine by the body's immune cells.

21.1.3 Tests for Food Allergy
There are many types of test to diagnose food Allergies that can be done by specialist hospital allergy units (e.g. IgE skin-prick and RAST tests).

The good thing about these tests is that when the result is negative, you can be 100% certain that you are not Allergic to tha food. Interpreting a positive result is not so straightforward, as it does not definitely mean an Allergy. So, these tests are more reliable when the result is negative than when it is positive.

21.1.3.1 Tests for Food Allergy that are NOT recommended
There are many tests that are offered by various companies, but these tests are not based on firm scientific facts and are therefore not recommended by healthcare professionals. They include (list from American Gastroenterology Association):

• Basophil histamine release/activation

• Lymphocyte stimulation

• Intra-dermal food injection

• Facial thermography

• Gastric juice analysis

• Endoscopic allergen provocation

• Hair analysis

• Applied kinesiology

• Provocation neutralization

• Allergen-specific IgG4

• Cytotoxicity assays

• Electrodermal test (Vega)

• Mediator release assay (LEAP)

21.2 Intolerance
This means that something is not being “tolerated” (i.e. just causing symptoms) but the immune system is not involved (e.g. burping or “repeating” with coleslaw or, feeling bloated after eating wheat). About 20 (or more) people out of every 100 have a food Intolerance (so, actually very common).

Another key difference, is that with an Allergy it is necessary to completely avoid the cause, whereas, with an Intolerance a little of whatever is the cause may be tolerated. If you are "Allergic" to cats, a kitten can still make you wheezy; but, if you don't "tolerate" cats, you might still find a kitten cute!

21.2.1 Common Foods causing Intolerance and Bloating with IBS
Food Intolerance is a common cause of IBS symptoms. This can happen when the gut is unable to make the enzyme required to digest the carbohydrate part of food, or when the enzymes get overwhelmed by too much of a certain food, leaving the carbohydrate free to pass undigested to the colon. An enzyme is like a molecular scissors that chops things up for better absorption. The cells lining our guts produce millions of these enzymes for that purpose.

Any carbohydrate that escapes digestion and reaches the colon becomes a fermentable carbohydrate. The by-product of carbohydrate fermentation includes fatty acids (can cause loose stools) and gas (can cause bloating).

There are several carbohydrates that are potentially fermentable in the colon.

21.2.1.1 Lactose: A common food Intolerance is to milk and milk products, which occurs as a result of an inability of the gut to produce the lactase enzyme that digests the naturally occurring sugar (lactose) in milk. This applies for all types of milk, whether from cow, goat or sheep.

Symptoms of lactose Intolerance can include tummy pain, bloating, loose stools, excess gas and rarely, constipation. Most people with lactose Intolerance usually tolerate a small amount of lactose in their diet from different sources e.g. some cheeses or yoghurt can be okay, but milk may be a problem.

An episode of food poisoning can affect the gut cells that make lactase. It can take a while for lactase production to get back to previous levels and for the individual to tolerate milk, etc again. Sometimes lactase production never returns.

Natural gut production of the enzyme lactose naturally falls in about two-thirds of people by adulthood. One person out of every eight in the UK has lactose intolerance; it is very much higher in the Chinese and Japanese (which is why dairy is not part of their cuisines).

21.2.1.2 Fructose: Sometimes referred to as 'fruit' sugar. It is actually one of several different types of sugar in fruit (and some vegetables, as well as honey). Fructose may also be present as a sweetener called high-fructose corn syrup (HFCS) in a range of foods and soft drinks.

Nature has given our tummies a strangely very complicated way of dealing with fructose. For this reason, the capacity of the intestine to absorb fructose is easily swamped. Consuming too much fructose can result in a lot of it ending up in the colon. Given enough fruit, everyone will get Diarrhoea and this is the reason.

For many people this is not a problem, but for others, bacterial fermentation of fructose in the colon causes excess 'wind', bloating, abdominal discomfort and loose, frequent stools.

21.2.1.3 Fructans: These are fructose molecules linked together in a chain like a string of beads. We can't break up the chains (i.e. digest them), which means we can't absorb them, so fructans end up in the colon, where they too then get fermented- and you know how that ends!

Foods that are high in fructans include artichokes, asparagus, leeks, garlic, onions and wheat.

21.2.1.4 Galactans: These are galactose (a type of sugar) molecules linked together in a chain like a string of beads (much like fructans). We can't digest the galactan chains either and so they also end up in the colon, where they are fermented.

Galactans are found in pulses e.g. baked beans, kidney beans, chickpeas.

21.2.1.5 Sugar alcohols: We cannot digest or absorb these food components, so they end up in the colon, where they are fermented. Sugar alcohols include sorbitol, mannitol and xylitol and are naturally present in some fruits and vegetables. Importantly, they are also used as low-calorie sweeteners in a range of foods, drinks and confectionery- sugar-free gum and snack-bars.

21.3 Natural chemicals in Food make us "React"
We wouldn't want to make life too simple by just limiting matters to Allergy or Intolerance. It's important to mention that some foods naturally contain chemicals that kick-off our immune cells, or that don't agree with some of us. These generally are easy to spot as the reaction (often an itchy rash or wheeziness) occurs whilst we eat. Some examples of foods and their chemicals are:

• Strawberries - histamine and salicylates

• Mackerel - histamine, scombroid toxin

• Parmesan, camembert, brie, chianti - histamine

• Preserved foods, tinned coconut milk, dried fruit- sulphites and salicylates

• Non-fruit teas, coffee, cherries, tomatoes, sharp green apples- salicylates

Does that mean we should avoid these foods? Absolutely not! If you've always eaten them and had no reaction (like 99% of us), they're fine.