What is an Allergy?

An “allergy” is an adverse immune reaction to a protein in our environment called an “allergen”. Common allergens include: pollen, dust mite, animal dander and foods such as nuts, eggs, milk, fish, wheat, soy, fresh fruits and raw vegetables.

It all begins with exposure – even if you have inhaled or swallowed an allergen many times before without incident, at some point, for complex reasons still being identified, the body flags it as an invader and readies itself for the next exposure by developing antibodies. You are now “sensitised” to the allergen.

The next time you are exposed to the allergen, your immune system responds, triggering an inflammatory response with the release of multiple chemicals, in particular histamine, in the lungs, skin, lining of the nose and intestinal tract and development of symptoms. The type of symptoms you experience depends on the allergy and the type of exposure. If you inhale pollen, for example, you may develop sneezing and wheezing as the airways are affected. Food allergy may lead to itching, swelling and irritation of the mouth/throat or even progress to full-blown anaphylaxis with airway closure and/or a drop in blood pressure. This can be fatal.

Rhinitis

Rhinitis is an inflammation of the lining of the nose and typically causes symptoms such as runny nose, itching, sneezing and nasal blockage. Rhinitis can be classified as allergic or non-allergic and the challenge is differentiating between the different types to allow selection of the correct drug treatment and to decide whether avoidance measures or immunotherapy would be helpful.

Allergic rhinitis is very common, affecting one in four people in the UK and may be  seasonal – due to pollens (i.e. “hayfever”), perennial – for example due to house dust mite, cats, dogs and moulds, or occupational – triggered by exposure to allergens such wood dust. Allergic rhinitis of any cause is a risk factor for the later development of asthma.

Non-allergic rhinitis can also be associated with asthma. The most common cause of non-allergic rhinitis is an acute (short-lived) viral infection. Less common chronic causes include:

• Environmental or occupational irritants. Dust, smog, passive smoke, fumes or strong odours, such as perfumes.
• Weather changes. Temperature or humidity changes can trigger the membranes inside the nose to swell and cause a runny or stuffy nose.
• Stress. Emotional or physical stress can trigger non-allergic rhinitis in some people.
• Infections. A common cause of non-allergic rhinitis is a viral infection such as the common cold. This type of non-allergic rhinitis usually clears up after a few weeks, but can cause lingering mucus in the throat (post-nasal drip). Sometimes, this type of rhinitis can become chronic, causing ongoing discolouration of the nasal discharge, facial pain and pressure (sinusitis).
• Foods and beverages. Especially hot or spicy foods. Drinking alcoholic beverages also may cause the nasal lining to swell, leading to nasal congestion. These reactions are commonly due to the additives/preservatives in the foodstuffs and alcohol.
• Certain medications. Including aspirin, ibuprofen and blood pressure medications, such as beta-blockers and angiotensin-converting enzyme (ACE) inhibitors. Also sedatives, antidepressants, oral contraceptives or drugs used to treat erectile dysfunction. Overuse of decongestant nasal sprays can cause a type of non-allergic rhinitis.
• Hormone changes. Changes in hormones due to pregnancy, menstruation, oral contraceptive use or other hormonal conditions such as an underactive thyroid.

Symptoms

The presenting symptoms of allergic and non-allergic rhinitis are often indistinguishable from one another but generally speaking non-allergic symptoms tend to be more nasal blockage and rhinorrhoea (excessive running of the nose), whereas allergic rhinitis is more associated with sneezing and itching.

Management

Rhinitis is common but frequently ignored or regarded as trivial, even by sufferers themselves. However it can reduce quality of life by impairing sleep and reducing performance at school or work. The diagnosis of non-allergic rhinitis is made after eliminating allergic causes and differentiation of the two diseases is crucial. Although many people can self-manage with over the counter remedies, an assessment by an allergist can help even the most severe cases by ensuring the correct diagnosis is made, appropriate medication prescribed and specialist treatments such as desensitisation (allergen immunotherapy) are considered. Furthermore, rhinitis and asthma often co-exist and untreated rhinitis can exacerbate asthma. It is important to treat the nose and lung as a single airway in order to manage both conditions effectively. As a Respiratory Consultant, Dr Ali will provide a full assessment of your lungs when treating your rhinitis.

Food allergy and additive intolerance

There are different kinds of adverse reactions to food – some are considered allergic and others are non-allergic. Those that are considered allergic are called food allergies.  Those that are non-allergic are called food intolerance.  When someone is having an adverse reaction, it is important to determine what is allergy and what is food intolerance.

Symptoms

Food allergies occur when your immune system reacts to a particular food or food additive.  This can range from a mild reaction, such as oral itch, to one that is severe and life-threatening (anaphylaxis). Chemically, it is believed that your body is responding to the proteins in the food. Unfortunately, even a very small amount of the protein can trigger a reaction. On the other hand, food intolerance usually causes symptoms such as diarrhoea, bloating and stomach cramps. This happens because the body has difficulty digesting certain substances in food, or because certain substances have a direct effect on the body in some way. The symptoms of food intolerance occur usually a few hours after eating the food, whereas allergic reactions happen much more quickly.

A small number of foods are believed to cause the majority of food allergies. The top eight food allergens are: eggs, fish (including cod and salmon), shellfish (including crab, prawn and lobster), tree nuts (including walnuts, almonds and cashews), peanuts, cow’s milk, soy and wheat.

Sometimes, ingestion of the offending food must be linked with something else called a “co-factor” (such as exercise, alcohol or use of non-steroidal anti-inflammatory drugs) to induce a reaction.

Also an allergy to one food sometimes results in an allergy to all foods of the same family.  For example, allergy to crab puts you at higher risk of being allergic to prawn and lobster. This is called “cross-reactivity”. Some patients have what is called “Pollen-Food” Syndrome or “Oral Allergy Syndrome”. In this condition, individuals with strong reactions to certain pollens will experience cross-reactivity with certain fruits and vegetables.

Management

Diagnosing food allergy can range from simple skin prick testing, to more complex testing such as a provocation challenge. Identification of a cause not only reduces risk but also anxiety. Dr Ali will provide advice on avoidance, refer to a specialist dietitian where appropriate and provide prescriptions for, and training on how to use adrenaline auto-injector pens.