Many early years settings are used to caring for children with allergies and intolerances, but they are conditions that can be hard to understand, and for the medical profession, they are not always easy to diagnose or treat. Last month the National Institute for Health and Clinical Excellence (NICE) issued new guidelines on identifying and treating allergies in children.
As a GP, I find parents often ask if their child's adverse reaction to food stems from an allergy. While this is a perfectly reasonable question, and an allergy may be the cause, it is worth remembering that adverse reactions to foods may occur without allergy. Other possible causes may be the body's inability to process foods, food poisoning through toxins or infection, or indeed chemical reactions rather like the side-effects of a drug.
Allergic reactions are an inappropriate reaction by the immune system in response to something in the food known as an allergen. It is thought that around 5 per cent of children suffer from food allergies, although this varies across the medical literature. Data has shown that peanut allergies are increasing, affecting four children per 1,000 in 1997 and eight in every 1,000 children in 2002.
Unsurprisingly, given the complexity of the immune system, a number of different disease processes can lead to food allergy. Broadly speaking, these immune processes may be divided into IgE mediated or non-IgE mediated.
IgE-MEDIATED ALLERGIES
IgE is medical shorthand for type E immunoglobulin, which is an antibody. Food allergies most commonly occur via this immune pathway that is otherwise referred to as a type 1 hypersensitivity reaction.
In this scenario, sufferers are initially exposed, or sensitised, to a food.
Further exposure, such as to peanuts or seafood, then triggers an allergic reaction.
It is not only food that may cause this type of reaction. Bee stings, for example, may also cause type 1 allergies. In addition, and rather peculiarly, exposure to certain pollens may predispose people to suffer from food allergies. This is because allergens in some pollens are very similar to those found in particular foods. For example, birch pollen allergy may predispose people to hazelnut allergy.
The IgE-mediated allergic reaction triggers the release of a number of chemicals, including histamine. Allergies of this type will generally become apparent in the early years of life, after weaning when foods are introduced.
There is some evidence to support that up to 40 per cent of eczema sufferers have an IgE-type food allergy.
Symptoms usually occur within a few minutes of ingesting the offending food. It is impossible to predict the severity of the reaction based on the food type alone. In most cases the symptoms are mild, with itching and swelling around the mouth, and a rash known as urticaria - commonly referred to as wheals or hives. Vomiting and diarrhoea may also occur.
More serious reactions are suggested by swelling of the lips, tongue and throat, which may cause difficulty in talking or even breathing. Other symptoms of anaphylaxis include wheezing due to spasm of the airways within the lungs.
Whether food allergies truly cause asthma, which is one of many causes of wheeze, is controversial. In its most severe form, type 1 hypersensitivity reactions will cause patients' blood pressure to fall to the extent that organs, including the brain, are deprived of sufficient blood supply.
Anaphylactic shock usually causes the patient to collapse and it is often fatal without emergency treatment. Asthma, a previous history of anaphylaxis and failure to treat with an adrenaline pen are the main risk factors for death during anaphylaxis.
NON IgE-MEDIATED ALLERGIES
Non-IgE mediated food allergies are equally important, but not as dramatic as IgE mediated reactions. This immune pathway is often described medically as delayed hypersensitivity or T-cell mediated immunity.
Some of the best-known conditions involving this type of food allergy are coeliac disease and milk protein allergies. To complicate matters, some foods may cause both IgE and non-IgE mediated allergies in susceptible people.
Coeliac disease is considered to be an under-diagnosed condition which occurs, in simple terms, due to an allergy to gluten. There is evidence to suggest that it affects in one in 100 people.
Coeliac disease can run in families and does indeed have a genetic link. It can present at any age and in a variety of ways. Infants will only show signs of disease after weaning and exposure to foods such as wheat.
Signs and symptoms of coeliac disease include failure to thrive, abdominal pain, diarrhoea and anaemia. Stool which floats and is difficult to flush away may also occur and is due to fat malabsorption. An intensely itchy rash that is associated with coeliac disease is called dermatitis herpetiformis. Irritability and vomiting may occur, and some children may appear thin and floppy.
The most common milk protein allergies are cow's milk and soya bean. Allergy to cow's milk proteins may either be IgE or non-IgE mediated and indeed, there may be children who have intolerance to cow's milk without a clear immune mechanism.
Unsurprisingly, symptoms will occur once exposure to milk proteins has occurred. Like most allergies, it may affect the skin, mouth, gut and lungs. Symptoms include urticaria, eczema, mouth swelling, diarrhoea and vomiting, wheezing and anaphylaxis. Bleeding from the gut and colic may also occur.
INTOLERANCES
One of the most common food intolerances is lactose intolerance, which occurs through an inability or reduced ability to process lactose-containing foods. Given that the underlying mechanism is a deficiency of an enzyme called lactase, rather than an immune disorder, it is not, strictly speaking, an allergy. In some cases, lactose intolerance may occur after a gut infection and it takes a while before lactase levels increase to normal levels.
Lactose is a sugar and is normally broken down by lactase to form glucose and galactose. Lactose intolerance causes lactose to build up in the gut, drawing water into the bowel by a process called osmosis, ultimately causing diarrhoea.
In addition, bacteria in the gut act on the lactose to produce lactic acid, making the stool acidic, which may damage the skin around the anus. Abdominal pain, bloating, vomiting and poor growth can also occur.
DIAGNOSIS
The diagnosis of an allergy or intolerance starts with taking a robust medical history and teasing out exactly what the symptoms are. Asthma, hay fever or eczema sufferers are arguably more prone to allergies, so these should be enquired about. Diet, age when the allergy started, how long it took from ingestion to onset of symptoms, duration of symptoms and response to elimination of particular food types are some of many important questions that may be asked by healthcare professionals.
Many doctors advocate an elimination diet to see if symptoms resolve. However, if there is a history of failure to thrive, severe allergic reaction, multiple allergies, blood in the stool or diagnostic difficulty, the doctor may refer the child to a specialist.
People with a suspected IgE-mediated allergy may then be offered skinprick testing or blood tests to look for IgE antibodies against specific allergens. If a non-IgE mediated allergy is suspected, specific tests may still be available, such as that for coeliac disease. Lactose intolerance may tested for by stool analysis.
TREATMENT
Treatment for food allergies and intolerances depends on the cause and the severity of the symptoms. Education and food avoidance plays a big role in managing these conditions. Mild allergic reactions may respond to antihistamines.
For severe allergic reactions, parents, teachers and children will need to understand when and how to use adrenaline pens. Delays in using them, often due to failing to carry them, is one of the leading reasons why people continue to die from anaphylaxis.
Patients with coeliac disease will need to be regularly monitored in hospital clinics as there is a risk if bowel cancer later in life, particularly in those who continue to ingest gluten-containing products.
Lactose intolerance will require a lactose-free diet unless it occurs secondary to a gut infection, in which case slow introduction to sugars over time is often all that is required. The risk of cow's milk allergy may be reduced by breastfeeding for at least four months, but this isn't always possible. If breastfeeding an infant with cow's milk intolerance, the mother's diet will have to be manipulated to exclude the offending proteins. Bottle-fed infants will require specialised formulas that do not contain cow's milk proteins.
Ultimately, if there are any concerns, the child should always be taken to see a doctor. However, most children will grow out of their condition and face a healthy and happy life.
Dr Raj Thakkar BSc(Hons) MBBS MRCGP MRCP(UK) is a full-time GP in Buckinghamshire
MORE INFORMATION
A summary of the new NICE guidance on allergies is at: www.nhs.uk/news/2011/02February/Pages/ new-NICE-guidance-for-child-allergies.aspx
