Allergy explained

Allergic disease is now very common and can be distressing to an individual. Symptoms can range from skin itching and swelling to nose blockage, asthma, food allergy to life threatening reactions. Expert diagnosis and management is essential.

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Allergic Rhinitis (Hayfever and Perennial Allergic Rhinitis)

The nose and sinuses have critical roles as the guardians of our airways (breathing tubes) protecting the lungs from breathing in harmful substances. The nasal-sinus apparatus performs this function by filtering and warming the air we breathe, and alerting the body when something may be harmful. As a result the nose is a very organised and sophisticated structure. The immune system in the nose is highly developed, allowing the nasal passages to react rapidly to particulate matter breathed in. If the nose is over-reactive to such inhaled material such as tree or grass pollen then allergic disease such as hayfever (termed seasonal allergic rhinitis) can result. The main symptoms people feel are nasal congestion and watery discharge along with irritability of the nose (sneezing and itch). If the allergy is to inhaled allergens that are prevalent all year round then chronic symptoms can occur (termed perennial allergic rhinitis), often described by patients as a feeling of a ‘constant head cold’. Allergy to house-dust mite droppings, cat and dog protein, horse hair or even cockroach droppings can all lead to perennial allergic rhinitis. Accurate diagnosis and treatment is essential, as allergic rhinitis can lead to other complications such as glue ear, sinusitis, exacerbation of asthma, cough and effect daily function such the ability to concentrate at work or even exam performance. Allergy desentisation (immunotherapy or ‘allergy shots’) can be very effective in selected individuals (see below).

Dust mites
Figure 1 House Dust Mites are a common cause of nasal and sinus symptoms that occur all year round.

Allergy and Eyes

Eye allergyEye symptoms of allergy are very common, particularly in hay fever. The manifestations are watery eyes, itching, burning (irritability), redness and sometimes puffiness around the eyes. It is very important to treat, as such symptoms lead to impairment of daily activity at work and school. Often treating the nose allergy can lead to a marked improvement in eye symptoms.

Food Allergy

Food allergyWhilst allergy to almost any food can potentially occur, allergy to certain food groups is more common. Milk and egg allergy are often out grown by 5 years of age. Seafood allergy is more common in adults than children and this could be rising due to the increasing popularity of seafood. There is often a high rate of cross reactivity between fish species and allergic reactions tend to be severe. People should avoid all seafood until seen by an allergist if seafood is suspected.

Fruit-vegetable-nut allergy is also important, common and becoming increasingly complex to diagnose and treat. Some forms of allergy lead to only mouth and throat symptoms. Here sensitisation (IgE) to tree and grass pollen leads to cross reaction with proteins with fruit, vegetables and nuts causing contact itch, swelling and irritation of the mouth/throat within minutes of consumption. Birch pollen allergen is the most important in terms of cross-reactivity and 75% of birch pollen positive patients have such symptoms. Birch may cross- react with apple, pear, cherry, peach, nectarine, apricot, plum, celery, kiwi, nuts, carrot and potato.

Primary plant-food allergy is separate and can present with life threatening symptoms (called anaphylaxis). For example allergy to lipid transfer proteins (LTPs) in apple and peaches is a worrying allergy in Italy and Spain. Caution is therefore needed when diagnosing the type of plant food-allergy. Fortunately, given our rapid advances in understanding how different parts of the food or other allergen contributes to different types of allergy, and using testing with recombinant allergen molecules, we are getting very good at arriving at an exact diagnosis of allergy in general.

Peanut Allergy

Peanut allergy is important as it can lead to very severe reactions. We do not know exactly why it is so common and why the allergy can be so severe. 20-30% of patients have accidental exposure despite strict efforts to avoid nuts. Thus allergic individuals need to be prepared for an emergency. Excellent asthma control is essential in such patients. Understanding what causes peanut allergy is important. Family history of peanut allergy is important and presence of other allergy is a risk factor for developing peanut allergy. There is no definite evidence that prenatal sensitisation from the maternal diet can lead to peanut allergy (shown in the Avon Longitudinal Study). In the Avon study, peanut oil (arachis oil) containing cream/lotion use on broken eczema skin was identified as an important risk factor for sensitisation, so such creams should be avoided. Always speak to the pharmacist and read the label on the tube.

Skin Allergy

Hives and swelling of the skin (termed urticaria and angioedema) is a troublesome condition. Often, the immune system related to allergy is involved in the condition, but only on a few occasions can certain foods or drugs be implicated as causal. We do not fully understand this condition, but it is very important to ensure an Allergist evaluates the condition. Exclusion of more rare but important causes such auto-immune disease should be undertaken.

Skin prick testing for allergies


This is the term used to describe the most severe form of allergic reaction. It happens when the immune cells involved with allergy release several chemicals or mediators that cause rapid leakage of fluid from vessels into tissues leading to swelling of the body and airway. Loss of vessel tone can cause the blood pressure to fall. Such changes can occur rapidly, sometimes starting with non-specific body itching but then rapidly progressing to swelling of the mouth, throat and breathing tubes. Food induced anaphylaxis will typically cause breathing compromise and it very important to always ensure you have optimal asthma control if there is a background of severe food allergy. Drug and venom induced anaphylaxis will typically lead to cardiovascular compromise and again can progress rapidly with symptoms of dizziness and collapse. There are several causes of anaphylaxis, as shown in the figure below. Bizarrely, exercise can be associated with anaphylaxis in individuals. Sometimes, the Allergist cannot always find the exact cause, and this is termed idiopathic anaphylaxis.

Reproduced from Sampson HA et al. J Allergy Clin Immunol 2005;115:584-591

Measures for patients at risk

  • Wear and carry appropriate identification of any important allergy
  • Ensure you are fully educated on avoidance measures and have a rehearsed action plan in place for any inadvertent allergen exposure. This should be through an experienced allergist.
  • Recognise a serious allergic reaction early.

Courtesy of ALK ABELLĂ’

Features of early anaphylaxis

No single symptom is diagnostic but should alert an allergic individual to activate the action plan rehearsed with their allergist

  • Ensure you can self-inject epinephrine (adrenaline) in case of an emergency.
  • Preventive desensitization (for Venom allergy) and pre-treatment should be discussed with an allergist.
  • If you have asthma, ensure your asthma control is always optimal.

The following literature references illustrate the wide and varied causes of anaphylaxis found.

Immunotherapy (Allergy Desentisation)

What is immunotherapy used to treat?

Injection immunotherapy (allergy desentisation) is generally restricted to severe summer hay fever that does not respond to other treatments and severe reactions to bee or wasp stings. Severe nasal house dust mite allergy and other animal allergy such as cat allergy are also sometimes treated this way, although the results here are less efficacious.

We cannot use injection immunotherapy in the UK when uncontrolled asthma is present or to treat multiple allergies.

How effective is injection immunotherapy?

Clinical studies report up to 75% reduction in symptoms and medication use in severe hayfever. The results are even better for individuals with severe bee and wasp venom allergy, with a 90% or more reduction in the risk of anaphylaxis if re-stung.

Oral (Sublingual) Immunotherapy

Oral-sub-lingual (under the tongue) form of immunotherapy called Grazax was licensed in the UK in 2007 for treating grass pollen induced hayfever. It is a tablet taken under the tongue which rapidly dissolves and gets absorbed. Any remaining amount is swallowed. Several large-scale double blind placebo controlled studies have clearly demonstrated the clinical efficacy and safety of Grazax sublingual grass-specific immunotherapy. The most recent data confirms that the marked improvements in disease severity are sustained even after the cessation of treatment. The first dose must be given by an Allergist, but the rest of the treatment can be taken safely at home. The recommended regime is to take Grazax everyday for a total of 3 years. Treatment should be started 4 months before the grass-allergy season.

Courtesy of ALK ABELLĂ’

Pre-Seasonal immunotherapy

A new therapeutic approach is to use an immunotherapy product for grass and tree allergy, named Pollinex Quatro (Allergy Therapeutics PLC), (also other allergy products available) that requires only 4 injections, each a week apart. This shorter and safe regime is possible as the allergen (grass or tree here) is combined with an agent that safely stimulates the immune system. A significant reduction of symptoms and requirement for medication (40-60%) has been shown in published trials.