Is it an allergy, an intolerance or a sensitivity? Understanding their differences and how to manage them.

Sniffing and sneezing and itchy, watery eyes are the classic signs of hay fever that many of us are familiar with. Some of us are also familiar with unpleasant digestive symptoms when we eat a certain type of food. But is it an allergy, intolerance or sensitivity?

In this blog post, we are going to try and unravel the confusing and often interchangeable terminology that is used to describe reactions to foods or environmental triggers, such as pollen.

What Are Allergies?

Allergies are immune system reactions to substances that would normally be considered harmless to most. These substances, known as allergens, can include foods, pollens, animal dander, mould or dust mites.

When someone with an allergy is exposed to an allergen, their immune system mistakenly identifies it as a threat. This prompts the release of chemicals such as histamine and leads to symptoms that may range from the mild, such as itching, hives or sneezing to the severe and sometimes life-threatening such as swelling, difficulty breathing, or anaphylaxis. Some of the most common allergies are:

• Food allergies: Cow’s milk, eggs, peanuts, tree nuts, wheat, soy, fish, shellfish, and sesame are among the most common triggers, especially in children.

• Seasonal allergies (hay fever): Triggered by pollen from trees, grasses, and weeds, especially in spring and summer.

• Other allergens: Animal dander, dust mites, and mould.

Allergic reactions can be immediate, causing symptoms within minutes to two hours, or they can be delayed appearing several hours or even days later.

How do I know if I have an allergy and what can I do?

You should always consult your GP if you suspect that you have an allergy. It is useful if you have kept a symptom journal, recording the pattern and severity of your symptoms and your GP will use this information, along with any pre-existing conditions such as asthma to start the diagnostic process.

Depending on your symptoms, the GP may suggest some targeted testing. Please be aware that this test will use targeted allergen components and is different to the type of allergy testing kits that you can purchase online. Commercial home tests are often indiscriminate, lack the context of your medical history and up to 60% of "positive" food tests don't reflect true allergies, meaning that you are at risk of making unnecessary and often restrictive changes to your diet.

If you are diagnosed with an allergy, your doctor may prescribe an appropriate medication that will help to calm the immune system, and it is likely that you will be advised to eliminate the allergen, such as peanuts or soy, from your diet.

There is some emerging evidence that suggests that certain nutrients may be able to help manage the severity of allergic symptoms, especially those associated with hay fever:

Vitamin C - can act as a natural anti-histamine and good sources include citrus fruit, berries, kiwi, broccoli and sweet peppers.

Quercetin - this flavonoid has anti-histamine and anti-inflammatory properties and is found in red apples, red onions, and herbs such as sage and parsley.

Omega 3 fatty acids - these fats have an anti-inflammatory effect and can help to modulate the immune system, and are most abundant in oily fish and walnuts.

What about intolerances?

Unlike an allergy, a food intolerance is not an immune response. Instead, it is as a result of the body’s inability to properly digest or process certain foods or food components, most often because the digestive system isn't producing enough of the enzyme needed to break down the food. This leads to unpleasant but generally non-life-threatening symptoms such as stomach pain, bloating, diarrhoea, and sometimes skin rashes. Common intolerances include:

• Lactose intolerance: This is the inability to digest lactose, the sugar found in milk.

• Gluten intolerance (also known as non-coeliac gluten sensitivity - see what we mean about interchangeable terminology?): This describes the difficulty digesting gluten. It is really important that we distinguish the difference between a non-coeliac gluten intolerance from Coeliac Disease, which is an autoimmune condition that attacks the small intestine in response to the ingestion of products containing gluten.

• Additive intolerance: Reactions to food additives like sulphites or artificial colours.

How do I get diagnosed and what happens next?

Again, keeping a symptom journal is a very useful tool to show to your GP. They may decide to refer you to a nutrition specialist who will guide you through an elimination and reintroduction diet, or you may be referred for a hydrogen breath test if they suspect that you may be lactose intolerant.

If you are diagnosed with an intolerance, you may be advised to reduce or eliminate that food from your diet, including foods that contain the ingredient that triggers your symptoms. Your GP might suggest using an over-the-counter enzyme, and while they might be useful, they are not a substitute for reducing or removing the trigger food.

If you are diagnosed with a food intolerance, make yourself familiar with food labelling to avoid cross-contamination and learn all of the different ingredients and names used for your trigger food.

As we've mentioned before, a food intolerance is the inability of the digestive system to break down a food or a component of your food and so focussing on your digestive health is especially important. You can do this by ensuring that your diet is well balanced, that you are eating regularly, and that you are chewing your food properly.

If you are removing dairy products, it may be advisable to have your vitamin D tested. This will indicate whether you have sufficient vitamin D in order to ensure that the calcium that you are eating in other foods such as green, leafy vegetables and small bony fish such as sardines is being properly utilised.

So what is a sensitivity?

This is a good question because the term “sensitivity” is less precisely defined by medical science. It is often used as an umbrella term for any adverse reaction to a substance that presents with symptoms that don’t fit neatly into the allergy or intolerance categories such as headaches, fatigue, or brain fog for example. However, as we've talked about above with an intolerance to gluten, this can also be termed as a sensitivity - it can be pretty confusing!

If it's a vague term, how do I know and what do I do?

Again, a food and symptom journal is going to be really useful when you discuss this with your GP. Food sensitivities can occur, for example, as a result of hormonal changes and so keeping your journal for an 8-12 week period can help you track how your symptoms might change.

The treatment offered by your doctor will very much depend on your symptoms. However, some adjustments to your lifestyle might be useful such as learning some stress management techniques or looking at your sleep routine to ensure that you are getting enough quality sleep - both stress and poor sleep are linked to poor digestive health and immune response.

To help you recap, we've put together this table with the main "features" of allergies, intolerances and sensitivities because understanding the differences between each diagnosis, is essential for the management of your symptoms.

As always, your GP is your first port of call but if you have been diagnosed and would like to know how our personalised approach to nutrition can support you to manage your symptoms, or if you are considering commercial testing, please do contact us to find out more.

	Allergy (e.g., hay fever, peanut)	Intolerance (e.g., lactose)	Sensitivity
Immune System	Yes (immune-mediated)	No	Sometimes
Onset	Minutes to hours (can be delayed)	Hours to days	Variable
Symptoms	Itching, swelling, hives, anaphylaxis, sneezing, watery eyes	Bloating, diarrhoea, stomach pain, rashes	Headaches, fatigue, brain fog, symptoms not usually associated with an allergy or intolerance
Severity	Can be life-threatening	Unpleasant, rarely dangerous	Usually mild
Diagnosis	Targeted allergy testing, medical history	Food exclusion, medical history	Often unclear

Sources: PMC/PubMed, NICE CKS, BNF, NHS, Foods Standards Agency, sciencedirect, Allergy UK