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Recognising allergy in infants and young children.

What is allergy?

Allergy occurs when our immune system (white blood cells) mistakenly identifies harmless things in the environment (eg, milk, egg, grass pollen, pets) as a danger to the body and mounts an aggressive immune response to them. This means that each time the affected person is exposed to a sufficient quantity of the environmental substance, they suffer symptoms caused by inflammation. The symptoms may be as diverse as itching, swelling, rashes, eye, nose, breathing and stomach complaints, and are caused by the person's own immune system.

It is normal for our immune system to make an active response to things like milk and pollen, but it usually correctly recognises that these are harmless and makes a type of immune response that does not lead to inflammation in the body (immune tolerance). Antibodies to food components, such as ovalbumin from hen's eggs or beta lactoglobulin from cow's milk, can be found in most people, but they are not the sort of antibodies that cause allergic reactions.

Allergy occurs when our immune system decides (for unknown reasons) to respond aggressively to something harmless, and allergy often involves a special type of antibody called IgE antibodies. While small amounts of IgE antibodies can be found in healthy people, a high level of IgE antibody can indicate allergy (see Figure 1).

Allergy has become more common in the last century and the illnesses associated with allergy are now the most common long-term illnesses in UK children. Eczema, food allergy, asthma, allergic rhinitis/conjunctivitis (hayfever) and other forms of allergy cost the NHS at least 1 [pounds sterling] billion per year and affect up to one third of children. Most affected children cope well with their allergy, but severe allergic disease can have a devastating impact and can even be fatal.

Effective treatments for allergy in children and infants

There are three different approaches that can be taken for treating allergy and the choice of treatment depends on a number of factors including the nature of the 'allergen', the frequency and severity of the allergic symptoms, access to the different modes of treatment, and patient/family choice.

Allergen avoidance

The most logical approach is to avoid the harmless environmental substance (allergen) that the body is responding to. This might be reasonably straightforward for a child with kiwi fruit allergy, but the most common allergens (milk, egg, dust mite, pollen) tend to be quite widespread in our environment and are difficult to avoid.

Despite careful avoidance strategies, children with food allergy tend to have some sort of accidental exposure, causing an allergic reaction every few years, and avoidance options are quite limited for airborne allergens such as pollen and dust mite. Over-zealous attempts to avoid allergens can become burdensome for the child, can interfere with normal social activities, and can be expensive for the family.

Most families do make some effort to keep their child away from the things that they are allergic to. However, the impact of this on symptoms is often quite limited, especially in the case of airborne allergens such as pollen.

Medications

The most common allergy treatments are medicines that suppress the allergic child's immune response to allergens, and thereby reduce symptoms. These are very widely used, and account for a significant proportion of the NHS costs of allergy. Typical treatments are:

* Topical steroids (as a nose spray, inhaler or skin cream)--effective at switching white cells off and suppressing the immune response locally

* Antihistamines (as nose spray, eye drops, tablet/liquid)--effective at preventing the itching and sneezing caused by histamine release from white cells. Non-sedating antihistamines are safer and preferred at all ages

* Other symptomatic treatments--emollient ointments for dry skin; bronchodilators for asthma; saline spray for nose symptoms; adrenaline for severe allergic reactions (anaphylaxis).

Allergen immunotherapy

In 1911, a doctor working at St Mary's Hospital in London discovered that repeated low-dose injections of grass pollen during early spring could prevent hayfever symptoms in people with grass pollen allergy. This became a popular treatment for allergic rhinitis/conjunctivitis (hayfever) and asthma during the second half of the last century, with many patients being given weekly and then monthly injections of pollen or dust mite to desensitise them and improve their allergy symptoms.

The attraction of the immunotherapy (or 'allergy shots') approach is that it can lead to a long-term reduction in symptoms even after the treatment course has finished--essentially a cure for allergy. The problem with this form of treatment is the small risk of a serious allergic reaction with each injection, which means very few UK centres offer the treatment.

In the 1980s it was discovered that drops or tablets under the tongue can have the same effect as allergen immunotherapy injections and are much safer. So tablet immunotherapy has become the preferred approach--availability on the NHS is limited due to cost considerations and this has only been proven to work for inhalant allergens such as pollens and dust mite. Allergen immunotherapy for foods has proven more difficult, but is being very actively studied at the moment and may become available in the future.

Many of us are interested in ways that we might prevent allergy from developing in the first place and this is of particular importance to those readers who see pregnant women and young infants in their practice. Mothers who already have an allergic child, or allergy themselves, often ask for advice about allergy prevention and food allergy in particular. At present, there is no specific recommendation for allergy prevention other than exclusive breastfeeding for four to six months, but many different approaches are being studied in trials around the world.

Table 1 summarises the known risk factors for food allergy, although these are likely to change as the field of food allergy research moves forward. I advise mothers to join a clinical trial if they have the time to do so, as any allergy will usually be detected and managed early and they may be given a treatment that can prevent allergy in their infant. In 2014, the Barrier Enhancement for Eczema Prevention (BEEP) trial will start, which focuses on different approaches to infant skincare for preventing eczema.

How can I recognise allergy?

Allergy can cause a surprisingly diverse range of symptoms, which often go unrecognised. In infants allergy can be particularly hard to recognise because many of the symptoms it causes are also seen quite commonly in healthy children. There are key differences between allergy to airborne substances and allergy to foods, which are summarised in Table 2.

The relationship between eczema and food allergy deserves special mention because earlyonset eczema is a good clue that a child may have food allergies and it is helpful if this can be picked up by parents and community health practitioners dealing with infants. Most food allergy is present before a child has knowingly been given the relevant food, due to microscopic exposures during pregnancy or early infancy sensitising the child. Most children with food allergy have eczema, and most children with troublesome eczema that starts early in their first year have a food allergy. The food allergy doesn't directly cause the eczema, but these two allergic conditions very commonly go together. Many parents are aware of this connection and seek allergy testing for their young child with eczema on the basis that they may need to avoid certain foods. The most common foods to cause a problem in this setting are milk, egg and peanut. It can be very hard to know whether an infant has a food allergy or not without testing --either allergy testing (skin prick, or blood IgE test), or giving them the food to see what happens. Parents often prefer a skin prick test because this is safer than experimenting with different foods.

Young infants with food allergy can also suffer from colic, vomiting or food aversion due to stomach inflammation caused by eating the food to which they are allergic. These symptoms are however very common in healthy children, so one has to be careful not to over-diagnose food allergy in young infants without doing any allergy testing. In young infants with eczema who are failing to gain weight appropriately, allergy testing/management is quite urgent, as the infant can become quite unwell in this setting but the symptoms respond to prompt exclusion of relevant allergens.

Allergy to airborne substances develops later in life, usually during the early primary school years--here typical symptoms are blocked nose, itchy eyes or episodes of coughing and wheezing. Sometimes, allergy to airborne substances can cause snoring, poor concentration or poor school performance. Wheezing in the first three years of life is not usually due to allergy, and most children who wheeze during this time do not have asthma symptoms during their school years.

Conclusion

Allergies are the most common long-term illnesses in children and often start in the first months of life. Early recognition and management of childhood allergies can be very helpful for affected children and their families. Key clues to the presence of allergy in a child are:

* Eczema in the first months of life (food allergy)

* Symptoms such as rash and swelling within 10 minutes of eating a food (food allergy)

* Nasal congestion or hayfever symptoms (inhalant allergy)

* Recurrent coughing or wheezing in primary school years (inhalant allergy).

CPD questions (please visit www.communitypractitioner.com/CPD to submit your answers)

1. Approximately how much do eczema, food allergy, asthma, allergic rhinitis/conjunctivitis (hayfever) and other forms of allergy cost the NHS each year?

A. 500,000 [pounds sterling]

B. 700,000 [pounds sterling]

C. 1 million [pounds sterling]

D. 1 billion [pounds sterling]

2. How many children in the UK are thought to be affected by some sort of allergy?

A. A quarter

B. A third

C. Half

D. Two thirds

3. What percentage of infants with significant eczema in the first year have a food allergy?

A. 0-10%

B. 10-20%

C. 30-40%

D. 50-60%

4. If there is a family history of food allergy, there is an increased risk of developing food allergy ... true or false?

A. True

B. False

5. Allergy often involves a special type of antibody called what?

A. IgA

B. IgB

C. IgE

D. IgN

6. What percentage of children whose sibling has peanut allergy, also have peanut allergy?

A. 10%

B. 15%

C. 35%

D. 40%

7. Typical symptoms of airborne allergy in children aged 3-4 onwards include eczema--true or false?

A. True

B. False

8. In 2014 the BEEP trial will start, which will focus on preventing:

A. Eczema

B. Hayfever

C. Food allergy

D. Pet allergy

9. Most food allergy is present before a child has knowingly been given the relevant food--true or false?

A. True

B. False

10. At what age does allergy to airborne substances typically develop?

A. At birth

B. At age one

C. Between two and three years

D. During the early primary school years

Robert J Boyle

MB ChB MRCP PhD

Clinical Senior Lecturer in Paediatric Allergy

Imperial College London

Honorary Consultant Paediatric Allergist

St Mary's Hospital Paddington

Correspondence: r.boyle@nhs.net

Robert Boyle's research programme at Imperial College London has been supported by the National Institute of Health Research, the Food Standards Agency, Asthma UK, Lincoln Medical (who market adrenaline autoinjectors), Allergy Therapeutics (who market immunotherapy treatments for allergy), Airsonett (who market a clean air delivery device) and Danone (who market specialist formulas for feeding children with milk allergy).

Table 1. Known and suspected risk factors for developing food allergy

Factor                              Effect

Family history                      Increased risk of food allergy
Specific genes                      Increased risk of food allergy
Eczema                              Increased risk of food allergy
Delayed dietary introduction        Possible increased risk of food
  of common food allergens            allergy
  (eg, egg, peanut, milk, sesame)
Caesarean birth                     Possible increased risk of food
                                      allergy
Early formula feeding               Possible increased risk of milk
                                       allergy and eczema

Factor                              Comment

Family history                      10% of children whose sibling has
                                       peanut allergy, also have peanut
                                       allergy
Specific genes                      Genes implicated include those
                                      affecting skin  barrier, enzyme
                                      degradation and immune response
Eczema                              50-60% of infants with significant
                                       eczema in the first year have a
                                      food allergy, usually egg
Delayed dietary introduction        Recent and ongoing studies are
  of common food allergens            testing early introduction for
  (eg, egg, peanut, milk, sesame)     food allergy prevention
Caesarean birth                     Recent studies suggest there may
                                      be no link
Early formula feeding

Table 2. Characteristics of allergies to foods and airborne substances

                                       Food allergy

                                       First year of life

Timing                                 Typically within 10-20
                                         minutes of exposure to
                                         the food, with exceptions

Typical symptoms      Skin             Hives (urticaria), swelling
                                        (angioedema), itching
                      Gut              Diarrhoea, vomiting, stomach
                                         pain
                      Respiratory      Sudden onset of sneezing,
                        system           coughing, noisy breathing
                                         (stridor), wheezing after
                                         food

                                       Airborne allergy

                                       Age 3-4 onwards

Timing                                 Harder to recognise when
                                         the exposure occurred, and
                                         for prevalent allergens such
                                         as dust mite, symptoms may be
                                         present continually
Typical symptoms      Skin             Eczema (occasionally)

                      Gut              None

                      Respiratory      Chronic blocked nose, runny
                        system           nose, itchy red eyes, asthma
                                         symptoms
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Title Annotation:PRACTICE: CPD
Author:Boyle, Robert J.
Publication:Community Practitioner
Geographic Code:4EUUK
Date:Oct 1, 2013
Words:2156
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