What is an Allergy?

Skin Analysis
18 Oct 2015

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What is an Allergy

When the term allergy was first introduced in 1906, it meant an adverse reaction to a food or other substance not typically regarded as harmful or bothersome.

For most people this is still what allergy means, although Health Practitioners use the word rather differently and this can be both misleading and confusing. Health Practitioners use the word allergy to mean an adverse reaction of the immune system to a substance not recognised as harmful by most people?s immune systems.

True allergies (for example allergies to pollens, dust mites, fish, shellfish or nuts) are typically associated with the formation of antibodies. Some people (Health Practitioners refer to these people as atopic) have an inherited tendency to this type of allergy and they tend also to be prone to asthma, eczema and hay fever; a condition known as atopy. In certain circumstances, and especially during the first few years of life, atopic people may develop immunoglobulin E (IgE) antibodies when exposed to an allergy-inducing protein in a process called sensitisation. When sensitisation has occurred, the allergy-inducing protein is referred to as an allergen and the resulting antibody (also a protein) as allergen specific IgE.

What is Intolerance?

Whilst Health Practitioners use the term allergy when referring to usually more visible and serious reactions of the immune system, the term intolerance is preferred when an adverse reaction is milder. The scientific term for an intolerance is non-allergic hypersensitivity.

Food intolerance can occur when the body fails to produce a sufficient quantity of a particular enzyme needed to break down a food and aid digestion. For example if a person suffers wind and bloating every time they consume milk or milk products they may be suffering from lactose intolerance, a condition caused by lack of the lactose-digesting enzyme lactase.

If a person suffers nervous system symptoms because of an amount of caffeine in a mug of strong coffee that would be tolerated by most people, this person would be suffering from a drug-like or pharmacological food intolerance. These can occur either because of an intolerance of chemicals naturally present in foods (such as theobromine in chocolate or tyramine in aged cheeses) or an intolerance of food additives such as sulphites or benzoates.

Whilst enzymatic and pharmacological food reactions only affect some people, toxic food reactions affect 100% of the population provided that a sufficient amount of the food is ingested. A good example is the false food allergy type of reaction that can occur when sufficient histamine accumulates in the flesh of spoilt tuna (scombroid reaction).

How Do You Know If You Have an Allergy?

The conventional allergy tests used by Health Practitioners depend on the presence of allergen-specific IgE antibodies. The most specific test would be an IgE blood. This test looks at a wide range of allergens from foods to plants, animals, mites, moulds and weeds. We offer this test to our patient if a serious allergy, such as urticarial or severe Eczema for example, are affecting the patient. Allergy tests are also useful if there is any confusion as to whether symptoms are being caused by true allergy or whether some other process is involved.

This is why allergy tests need to be interpreted by a healthcare professional qualified in allergy, who will interpret the results in light of an allergy-focused history.

Are There Other Tests For Food Intolerance?

With the exception of lactose intolerance, and IgG blood test would be also available. Recent scientific studies pointing to a delayed type food allergy in which the immune system is involved even though allergen-specific IgE is not present. For this reason we offer also an IgG food intolerance panel which involves also blood testing looking at a wide range of foods, so to investigate certain medically unexplained symptoms, which might be related to a delayed form of food allergy which appears to be involved in a number of gastrointestinal and skin conditions. Studies that have used food exclusion followed by blinded and placebo-controlled food challenge, have suggested that this kind of mechanism may apply in some cases of skin conditions, migraine, arthritis and irritable bowel syndrome.

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