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This module covers common allergies, how to manage them and future treatments

Update Module1790
From this module you will learn:
  • Common mild to moderate allergies that are encountered in the pharmacy every day
  • How to counsel patients on avoidance of allergens and provide suitable OTC advice
  • What to do in the case of severe allergic reactions
  • Future treatments for allergies

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Allergies are one of the most common chronic conditions in today’s society. Approximately one in four people in the UK are affected by an allergy at some stage in their life – and this figure is increasing.

An allergy is the response of the body’s immune system to an external stimulus or allergen. In the majority of cases, allergens – such as pollens, foods and house dust mites – are usually harmless.

Allergies are more common in children, with many growing out of their allergies as they get older – a process that is not particularly well understood. However, adults can also develop allergies later in life.

Allergies are classified into those that are immunoglobulin E (IgE)-mediated and those that are not. In IgE-mediated allergic reactions, the body produces IgE antibodies, which bind to the surface of mast cells. Mast cells line body surfaces and alert the immune system when a local infection has occurred. Mast cells become IgE-sensitised, and on first encounter with an allergen they will not produce the physical symptoms of an allergy.

However, when these mast cells encounter the same allergen for a second time, they become activated and secrete chemical mediators, such as histamine, which are released into the immune system, resulting in the symptoms of an allergic reaction.

Most allergic reactions are mild to moderate and can be self-managed. However, severe allergic reactions occasionally occur and can be fatal. The consequences of IgE-mediated mast cell activation depend on the dose of the allergen and its route of entry into the body. For example, symptoms such as a runny nose, with itching and sneezing, can occur on the inhalation of pollen.

Non-IgE mediated allergies are less well understood and are thought to involve multiple cells, which are part of the immune system and react to the presence of an allergen. The symptoms tend to occur some time after contact with the allergen, making it difficult to identify the cause.


People often mistake sensitivities and intolerances for an allergy. An intolerance is a reaction in the body that does not involve the immune system or IgE antibodies. Intolerances – to certain foods, for example – can have a significant impact on day-to-day life.

Reactions are often delayed and are frequently gastrointestinal in nature – such as bloating, diarrhoea and constipation – and can contribute to irritable bowel syndrome. In addition, these reactions may precipitate certain skin conditions, such as eczema, and can even lead to joint pain.

Food intolerances can be difficult to diagnose as reactions can be mild and caused by several different foods, producing multiple symptoms. In contrast, a sensitivity is an exaggeration of the normal effects of a substance – for example, caffeine in a cup of coffee may cause palpitation and trembling.

Common allergies

Hayfever This allergy to grass and tree pollen is also known as seasonal allergic rhinitis. Hayfever is often more prominent in spring and summer, when the pollen count is high. Common symptoms of hayfever include sneezing, a runny nose and red, itchy eyes. Pharmacists can recommend preventative measures such as:

  • staying indoors and keeping windows closed when the pollen count is high (more than 50 grains per m3 of air)
  • wearing wrap-around sunglasses to prevent pollen getting into the eyes when outdoors.

Dust mites An allergy to house dust mites is extremely common and is associated with asthma, eczema and perennial allergic rhinitis. Allergy to dust mites may trigger asthma symptoms, causing tightness of the chest, coughing and wheezing. Red, itchy or teary eyes can also be a symptom, as well as sneezing, a runny or blocked nose, and urticaria.

Preventative strategies for house dust mite allergy include:

  • choosing hardwood or vinyl floors instead of carpets
  • cleaning cushions, pillows and curtains regularly by washing or vacuuming
  • using a vacuum cleaner fitted with a HEPA (high-efficiency particulate arrestance) filter – this traps more house dust mites than normal filters
  • regularly wiping surfaces with a damp cloth.

Animal dander Dog and cat allergens are found in the saliva, sweat, urine, coat hair and skin cells of these animals, and are often spread during grooming.

Symptoms can include sneezing, a runny or blocked nose, facial pain (caused by congestion), coughing and tightness of chest, watery, red or itchy eyes, as well as urticaria. Avoiding exposure to pets is often the best preventative measure for those with allergies to animal dander.

Mould Spores produced by household mould are also a common allergen. Pharmacists can recommend keeping the home dry and well-ventilated, and also removing any indoor plant pots to help prevent allergic reactions. Symptoms include sneezing, watery eyes and a runny nose.

Food Common food allergies include nuts, fruit, shellfish, eggs and cow’s milk. Reactions range from mild to severe, and the most common symptoms are gastrointestinal in nature, such as vomiting or stomach cramps. However, the respiratory tract and cardiovascular system can also be affected, resulting in:

  • wheezing and shortness of breath
  • swelling of the tongue
  • dizziness
  • a weak pulse
  • anaphylaxis, in severe cases.

If there is a risk of severe reaction, pharmacists can advise patients to wear a medical alert bracelet and carry an adrenaline pen. For young children, a pharmacist can also advise parents to leave a spare adrenaline pen in schools in case of emergency.

Medication Common medications that cause allergies include ibuprofen, aspirin, arachis oil (peanut oil) and certain antibiotics, such as penicillin. Asthmatic patients are more likely to suffer an allergy to aspirin and it is necessary to be observant when these patients buy combination products, as they may contain aspirin.

Wearing a medication alert bracelet may help prevent a potentially life-threatening situation if a patient is already being treated for an acute illness.

Latex Latex found in rubber gloves and condoms can cause allergic contact dermatitis. This allergic reaction can produce blistering, weeping, redness and itching of the skin. These reactions are not life-threatening, but they can be itchy and uncomfortable.

For latex allergy, the best management option is avoidance of the allergen and using non-latex alternatives, such as PVC household gloves.

Household chemicals Detergents and hair dyes can cause local symptoms of allergic contact dermatitis, and may also cause systemic symptoms, such as urticaria, a general feeling of being unwell, malaise and, in severe cases, anaphylaxis.

Avoidance of the allergen and reducing exposure will help prevent contact dermatitis from occurring. Emollients can be recommended for the treatment of dry and scaly skin if this occurs.

For skin that is very sore, red and inflamed, pharmacists can recommend a mild topical corticosteroid, such as hydrocortisone cream or ointment 1%, to be applied thinly one to two times daily for a maximum of seven days. In moderate to severe cases, stronger topical corticosteroids can be prescribed by a GP.

Treatment of allergies

There is currently no treatment to prevent allergies, but over-the-counter (OTC) medications can ease symptoms. Nasal and ocular symptoms of seasonal and perennial allergic rhinitis and urticaria can be managed with non-sedating antihistamines such as cetirizine or loratadine, both 10mg once daily.

OTC nasal sprays or decongestants can reduce nasal symptoms, while allergy relief eye drops containing 2% sodium cromoglicate can help those experiencing red, itchy and sore eyes. It is important for pharmacists to counsel patients on the different methods of allergen avoidance and prevention.

Diagnosing allergies

The cause of allergy is not always obvious – in these cases, allergy testing may be beneficial. Skin prick testing is a safe and simple procedure that is commonly used to test for allergies. A tiny amount of allergen is introduced onto the skin, usually on the forearm, causing a small localised reaction, which presents as a wheal-and-flare. A positive response to an allergen will indicate an allergy.

Blood tests may also be carried out in conjunction with skin prick tests to confirm diagnosis of an allergy. This involves analysing blood for anti-IgE antibodies produced in response to an allergen.

For contact dermatitis, patch testing may be carried out by a dermatologist. Small amounts of allergens are added to small metal disks and are applied to patches on the skin, usually on the upper back. After 48 hours, the skin is then monitored for a reaction to any of the allergens.

With food allergies, patients may be asked to eliminate certain foods from their diet. These foods are then slowly reintroduced after several weeks to see if a reaction occurs.

Challenge testing may also be used to diagnose food allergy. This involves giving patients the food they are suspected to be allergic to in increasing amounts to test for a reaction. This test involves more risks as it could cause a severe allergic reaction, so should only be carried out under close medical supervision.


Severe allergic reactions can result in anaphylaxis. The UK resuscitation guidelines define anaphylaxis as a severe, life-threatening, generalised or systemic hypersensitivity reaction.

These reactions – often caused by allergen exposure – are generally characterised by life-threatening airways and/or circulation problems, as well as mucosal changes. Anaphylactic reactions occur rapidly and should be dealt with as a medical emergency. The symptoms can include:

  • generalised flushing of the skin
  • hives (nettle rash) anywhere on the body
  • swelling of throat and mouth
  • difficulty in swallowing or speaking
  • alterations in heart rate
  • severe asthma
  • abdominal pain, nausea and vomiting
  • sudden feeling of weakness
  • light-headedness (caused by a sudden drop in blood pressure)
  • collapse and unconsciousness.

The most commonly identified triggers for anaphylaxis include food, medicines and venom from an animal bite or sting. The triggers vary with age – food is more commonly associated with anaphylaxis in children, while medicines are more commonly associated with the elderly.

Adrenaline (epinephrine)

Adrenaline is an alpha-receptor agonist that reverses peripheral vasodilation and oedema. It is used as the first line of treatment for an anaphylactic reaction and works best if given as soon as symptoms are detected. Adverse effects are rare when given as an intramuscular (IM) dose.

The thigh is a commonly used IM route for an adrenaline injection. The recommended dose for adults and children over 12 years is 500 micrograms IM (0.5ml of 1:1000 adrenaline).

For children aged six to 12 years and for those over 12 years who are small or prepubertal, the recommended dose is 300 micrograms IM (0.3ml of 1:1000 adrenaline). For children up to six years, the recommended dose is 150 micrograms IM (0.15ml of 1:1000 adrenaline).

The plasma half-life of adrenaline is two to three minutes, so the IM dose of adrenaline can be repeated if there is no improvement in the patient’s condition, and further doses can be given at five-minute intervals according to the patient’s response.

Adrenaline can also be administered via an intravenous route, but this has greater risks and should only be considered by trained specialists in an intensive care setting.

Patients are often prescribed two adrenaline auto-injectors and are encouraged to carry these at all times. Pharmacists should be aware and familiar with the use of the commonly prescribed auto-injectors in case of an emergency in the pharmacy.

More information can be found at Pharmacists should counsel patients on the use of auto-injectors, as well as the importance of checking expiry dates, as these products are less effective when out of date.

Future treatments for allergies

Food oral immunotherapy (OIT) is a current hot topic as a potential future treatment for allergies. In studies of this treatment, very small amounts of the allergenic food are introduced into the diet, then gradually increased over a short period of time until a target dose is reached.

A study of a clinical trial published in the Lancet showed that this treatment had positive results for children with peanut allergy, with 84% of allergic children eating approximately five peanuts a day after six months of desensitisation. However, severe reactions have been reported during these trials and they have also been associated with a high rate of adverse events. The long-term effects of OIT are not well-known because the trials are ongoing.

Sublingual immunotherapy (SLIT) is similar to OIT, but in this treatment a small amount of liquid is held under the tongue for two to three minutes and then swallowed. Again, the dose is increased gradually over time and the patient should become desensitised to the allergen. Although results of SLIT studies have not been as robust, fewer adverse reactions have been reported.

Another treatment being investigated is epicutaneous immunotherapy (EPIT). This involves applying a small patch containing the allergen to the skin. Over time, increased exposure should cause desensitisation of the immune system to the allergen. Ongoing trials are also being conducted into subcutaneous immunotherapy (SCIT).


Tips for your CPD entry on allergies

Reflect How do immunoglobulin E (IgE)-mediated and non IgE-mediated allergic reactions differ? What are the symptoms of anaphylaxis?

Plan This article contains information about common mild to moderate allergies often encountered in the pharmacy. Counselling patients about allergen avoidance, providing OTC advice and what to do in the case of severe allergic reaction is also discussed.

Act Find out more about allergies on the Allergy UK website at

Read more about common allergies such as hayfever and dust mite allergy as well as advice for reducing exposure to allergens on the Allergy UK website at and at

Revise your knowledge of the treatment of allergy from the BNF Section 3.4 Antihistamines, hyposensitisation and allergic emergencies

Find out more about anaphylaxis by reading the factsheets on the Anaphylaxis Campaign website at

Evaluate Are you now confident in your knowledge of the symptoms and management of allergies? Could you give advice to patients about avoiding allergen exposure and what to do in cases of anaphylaxis?




Janeway CA Jr, Travers P, Walport M, et al. Immunobiology: The Immune System in Health and Disease. 5th edition. New York: Garland Science; 2001. Effector mechanisms in allergic reactions.



Take the exam

Suman Merag Shah, Community pharmacist

Come on c & d, start aIf 500mcg adrenalineI/M is the reccomendation for adult and owner 12 years olds, why are we seeing 300 mcg epipens being prescribed all the time for this age group, and also the wrong dose for under 12, and under 6 years old. 

Come on c & d start a campaign on behalf of pharmacy to correct this. Pharmacy for the good of public health.

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