Food allergies have become increasingly common these days. But just how prevalent are they? Is it just that we are more aware of them or are they really on the increase?
The fact that food allergies are appearing in very young children confirms that the increased incidence is real and not just attributed to a greater awareness and referral. The exact prevalence is unknown. Amazingly, there is no requirement for GPs to report severe allergic reactions (anaphylaxis) to a national register. However, it is estimated to affect between one and two per cent of the population and certainly is more common in children, especially pre-school children. Fortunately, the majority of children 'outgrow' their allergies.
Common causes
Peanuts, tree nuts, fish, shellfish and eggs are the most common causes of severe allergic reactions and are well known. But sesame, which has recently been added to that list, is less well recognised. It is not yet as common as peanut allergy, but reactions can be every bit as severe.
Allergic reactions to milk, soy, wheat and other cereals tend to be of less severity, but serious reactions can occur, particularly in young children. Only a minority may suffer a severe reaction, so the risk should be kept in perspective. In other words, don't panic.
Sesame
Sesame allergy deserves special attention because the allergen is difficult to avoid and reactions can be very severe and are evidently increasing. There is no research being carried out, so the prevalence is unknown. A 1996 Government report estimated that about one in 2,000 people are affected. I believe this figure could be much higher. Some peanut-allergic children have developed sesame allergy. Parents may be unaware of the widespread use of sesame seed and oil and as a result, there may be under-reporting of allergic reactions to sesame because peanuts or nuts may be blamed.
In Australia, where sesame has only recently been introduced into the diets of infants, sesame allergy has increased markedly and is now the second most severe food allergy after peanuts. In France, a striking increase has also been noted. As a result, warnings have appeared in the medical literature advising that sesame should not be included in the diets of young children.
In the light of this, it is surprising to find that sesame is now being included in recipes specifically targeted at babies and young children. Hummous, for example, has been recently recommended for babies in a well-known parenting magazine. Even more surprising is the marketing of Nestle Junior Sesame Sticks, specifically targeted at toddlers from one year old. Sesame is no longer confined to bakery products, exotic recipes and vegetarian diets (see box).
Cow's milk
Cow's milk allergy (CMA) is quite common in infants. Symptoms include widespread rashes, diarrhoea and wheezing. Anaphylaxis may occur in a minority of cases. Medical advice is essential before switching to alternative infant foods. Infants allergic to cow's milk may also react to goat's milk. Because CMA is common, milk-based substitutes are readily available. Fortunately, the vast majority of infants 'outgrow' milk allergy and other childhood allergies. The ones that are likely to persist are peanuts, tree nuts, sesame, fish and shellfish.
There are many theories as to why allergies are on the increase. For example, changes in lifestyle, exposure to antibiotics and less exposure to bacteria (a child's immune system may be more prone to allergies), exposure to pollutants and changes in diet.
I believe that diet plays an important role. Breastfeeding is no longer as popular as it was and this decline may be affecting the immunity of babies. Weaning foods are introduced early and, as well as sesame, they may contain other potent allergens. In older children, the increasing popularity of fast-foods, for example sesame seed burger buns and oriental foods, should be considered a risk factor for developing sesame allergy.
Allergies tend to run in families. Although atopic individuals (those with allergies, such as asthma or eczema, or a family history of allergies) are more likely to develop allergies very early in life, this is not always the case. Sesame allergy can develop at any age, irrespective of atopy. Indeed, young children who are not atopic have become allergic to sesame.
Allergy or intolerance?
The hallmark of a true food allergy, which is far less common than food intolerance, is its rapid onset. A child who develops an itchy rash (urticaria) and swelling of the lips within minutes of eating a certain food, is allergic to it. Medical advice is essential if this
happens, because the next time the food is eaten the reaction may be more severe.
Fortunately anaphylaxis, which is the most serious type of allergic reaction, is rare, but it can be fatal if emergency treatment is not carried out.
Symptoms can include urticaria (hives, nettle-rash); itching and swelling of lips, mouth, tongue and throat; asthma; palpitations; vomiting and a rapid drop in blood pressure which can result in fainting or loss of
consciousness.
Food intolerance, which is less serious than food allergy, often involves several different foods. Reactions are not immediate and a child may experience a variety of symptoms, including diarrhoea, migraine, bloating, abdominal and muscular pains.
An elimination diet usually identifies the culprit food, but seek medical advice before excluding any foods.
What to do
The Government advises families with a history of allergies to avoid peanuts during pregnancy and while breastfeeding and to introduce peanuts into a child's diet from the age of three. I believe it is wise to avoid sesame too. Encourage parents to seek their GP's advice if they are atopic, as there may be other allergens they should avoid.
Management
Once a severe food allergy has been identified, the only effective treatment is avoidance of the allergen, which must be backed-up by rescue treatment for use in emergencies. Children at risk of severe reactions are likely to be issued with an EpiPen adrenaline auto-injector. Antihistamines may also be prescribed. A MedicAlert emblem identifying their condition is essential.
Nurseries should advise parents of children at risk of severe reactions to ask their GPs for referral to a specialist allergy clinic, where the appropriate skin prick tests and blood tests can be carried out and the family will be instructed on the use of adrenaline. NW
Maggie Spirito Perkins, allergic to sesame herself, is the author of Sesame Allergy, the first review
of its kind in the UK (see The Pharmaceutical Journal,
May 1998 or the Royal Pharmaceutical Society's website at www.rpsgb.org.uk)
