10 of your allergy questions answered - May 2023

I get a lot of DMs through various social media platforms and thought I would share some of the questions I have been asked and their answers. With any of the more technical questions the answers have been as simplified as possible.

1 - What is an allergen?

An allergen is a protein that can cause an allergic reaction in some people. Allergic reactions can include severe life-threatening symptoms like anaphylaxis and difficulty breathing. Less severe symptoms can include itching, swelling, hives, nausea and vomiting.

2 - What are the Top 14 Allergens?

There are 14 allergens that food businesses must inform customers about if they use them as ingredients in the food and drink they provide.

These are

    Cereals containing gluten (like wheat, rye and barley)
    Sulphur Dioxide and Sulphites
    Tree Nuts (almonds, hazelnuts, walnuts, Brazil nuts, cashews, pecans, pistachios and macadamia nuts)

3 - Why are there only 14 Allergens?

In 2003 12 top allergens were covered in Annex IIIa of the EU directive 2003/89/EC which covers the labelling of allergens in food.

The original 12 in 2003 were

    Cereals containing gluten
    Sulphur Dioxide and Sulphites
    Tree Nuts

EuroPrevall was a large-scale study which launched in 2005 across Europe to inform on the bigger picture surrounding the incidence of allergic reactions to food in different European countries. It advised on the effect of allergies on the quality of life of sufferers, standardised allergy diagnosis and worked towards making standardised food labelling across the EU.

In 2011 EU Regulation 1169/2011 was published and Molluscs and Lupin were added to the original 12, taking the number of allergens to be labelled up to 14.

4 - How do I read food labels with a food allergy?

In the European Union (EU) it is a legal requirement that all food must be labelled with the Top 14 allergens. These are most commonly labelled in bold.

The term ‘may contain’ sometimes appears on packaging. This is called precautionary allergen labelling and indicates that the food may have been cross contaminated with the allergen. ‘Not suitable for…’ is another precautionary allergen label. These products are not suitable for people with severe allergic reactions and anaphylaxis.

5 - What is the difference between allergy and food intolerance?

A food allergy is when the body’s immune system reacts unusually to specific foods and produces antibodies called immunoglobulin E (IgE). Even tiny amounts of the offending food can trigger an allergic reaction.

Food intolerances are caused by problems with the metabolic system which usually means that there is an enzyme deficiency which causes certain chemicals to build up in the body as they are not being process, digested or removed properly. You are more likely to be suffering from a food intolerance than an allergy.

6 - What are Molecular Weights and what do they mean?

Most of my pages have lots of professional articles for each allergen, you may have noticed that those with specific allergens often mention the molecular weights of allergens.

Molecular weights are the measures of how heavy the molecule is. They are usually measured in kilodaltons (kDa). Knowing the molecular weight of an allergen can help identify and characterise allergens and their IgE-binding epitopes, which is the part of an antigen that is recognised by the immune system.

For example,
2S seed storage proteins are low in weight, between 7 and 16kDa.
11S seed storage proteins are 29 to 60kDa in weight.
7S seed storage proteins are heavier, weighing between 44 to 64 kDa.
(This information is taken from the WHO Allergen Nomenclature Database).

7 - What is Component Resolved Diagnosis?

Component Resolved Diagnosis (CRD) is a method that uses molecular weights to measure the specific IgE antibodies to different allergens or their components in the blood or skin.

Peanuts for example, have 18 allergens and they are not all the same weight and type. You may be allergic to just one of the allergens or a combination of them.

CRD can help predict the severity of the food allergy. Ara h 2 in peanut allergy is a 2S seed storage protein – which is associated with more severe allergic reactions and is a protein which is not easily damaged by heat or processing. Other allergens are associated with lower risk of clinical reactions, such as Ara h 8, which is a Bet v 1 protein, which is more likely to give oral allergy type symptoms which are less severe and unlikely to cause anaphylaxis.

8 - Why can allergies start so suddenly?

Allergies can start suddenly at any age, even if you have never had a problem with them before. The exact reason why this happens is not fully known, but there are some possible factors that may trigger or contribute to the development of allergies.

These include.

- A change in the environment, like exposure to new pollen types, dust mites, mould or animals.

- A change in your diet, eating a new food or a food you haven’t eaten in a long time.

- Changes in your immune system, such as infections, stress, hormonal fluctuations, pregnancy, or aging, which may make your body more sensitive or reactive.

- Use of certain prescription drugs and antibiotics can alter the balance in your gut and affect your immune system (these are more commonly food intolerances, as many drugs can affect digestive enzyme production).

9 - What is the IgE Scoring System?

When blood is taken for an IgE allergy it is tested for the number of antibodies to a particular allergen or group of allergens. The test results are usually reported in kilounits of antibody per litre (kU/L). The normal range of IgE in the blood varies from person to person, but generally, a test is considered positive if the allergen specific IgE level is greater than 0.35 kU/L.

There is not a standardised scoring system to describe the severity or level of an allergic reaction. The results from the blood test have to be reviewed along with the past medical history, skin prick tests and any food challenges.

Some systems are simply graded.

- Negative (under <0.35 kU/L)
- Weak Positive
- Positive
- Strong Positive

Others have more defined grades.

• Grade 0 = <0.35 kU/L (negative)
• Grade 1 = 0.35-0.7 kU/L (weak positive)
• Grade 2 = 0.7-3.5 kU/L (positive)
• Grade 3 = 3.5-17.5 kU/L (positive)
• Grade 4 = 17.5-52.5 kU/L (strong positive)
• Grade 5 = 52.5-100 kU/L (strong positive)
• Grade 6 = >100 kU/L (strong positive)

These units are arbitrary and each lab or clinic will have varying ways of categorising and grading your allergic reactions.

A diagnosis of “Grade 6” or “High Positive” allergy can still not accurately predict that the person will have a severe or life-threatening allergic reaction. The best indicator of the severity of reactions is the past medical history, these scales can just be used as a guideline.

10 - Are allergies genetic?

Yes, allergies can be genetic to some extent. Genetics are not the only factor that influences whether a person will develop allergies or not. Other factors such as diet, environment, exposure to allergens, and infections are likely to play a role.

This does not mean a child will inherit the same type or severity of allergy as their parents. For example, a parent with a peanut allergy may have a child with a milk allergy or no allergy at all. It is common for parents to have children with different allergies to each other or to have one child with allergies and others with none.

Currently the research has shown that some genes are involved in regulating the production and function of IgE and other immune cells that cause allergic reactions but, the exact genetic mechanisms of how allergies are inherited are still not fully understood.

If you want to read the next 10 allergy questions, which are more personal you can read that HERE.

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Let me know if you liked this style of blog post – I already have a couple of questions set up for the next one, but if you have any burning questions, you can contact me on any of the social media platforms at the bottom of the page – Thanks, Jemma.

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