Slievemore Clinic, Old Dublin Road
Stillorgan, Co. Dublin
Contact details
Contact details
Anaphylaxis is a severe allergic reaction - the extreme end of the allergic spectrum. The whole body is affected, often within minutes of exposure to the allergen but sometimes after hours. Peanut allergy and nut allergy are frequently severe and for that reason have received widespread publicity. Causes of anaphylaxis also include other foods, insect stings, latex and drugs, but on rare occasions there may be no obvious trigger.
Nobody would necessarily experience all of these symptoms.
Some people find that the allergy symptoms they experience are always mild. For example, there may be a tingling or itching in the mouth, or a localised rash - nothing more. This is not serious in itself, and may be treated with oral antihistamines. However, in some cases symptoms may become worse over time. It is wise in all cases to make an appointment with the doctor and seek a referral to a specialist allergy clinic.
If there is marked difficulty in breathing or swallowing, and/or a sudden weakness or floppiness, regard these as serious symptoms requiring immediate treatment.
Pre-loaded adrenaline injection kits are available on prescription for those believed to be at risk. These are available in two strengths - adult and junior.
The injection must be given, as directed, as soon as a serious reaction is suspected and an ambulance must be called. If there is no improvement in 5-10 minutes, give a second injection.
Any allergic reaction, including the most extreme form, anaphylactic shock, occurs because the body's immune system reacts inappropriately in response to the presence of a substance that it wrongly perceives as a threat.
An anaphylactic reaction is caused by the sudden release of chemical substances, including histamine, from cells in the blood and tissues where they are stored. The release is triggered by the reaction between the allergic antibody (IgE) with the substance (allergen) causing the anaphylactic reaction. This mechanism is so sensitive that minute quantities of the allergen can cause a reaction. The released chemicals act on blood vessels to cause the swelling in the mouth and anywhere on the skin. There is a fall in blood pressure and, in asthmatics, the effect is mainly on the lungs.
During anaphylaxis, blood vessels leak, bronchial tissues swell and blood pressure drops, causing choking and collapse. Adrenaline (epinephrine) acts quickly to constrict blood vessels, relax smooth muscles in the lungs to improve breathing, stimulate the heartbeat and help to stop swelling around the face and lips (angioedema).
If you have suffered a bad allergic reaction in the past - whatever the cause - then any future reaction may also be severe. See your GP and request a referral to an NHS allergy clinic. If you have asthma as well as allergies a referral is particularly important. Where foods such as nuts, seeds, shellfish and fish are concerned, even mild symptoms should not be ignored because future reactions may be severe. This also applies to drugs, insect stings or latex. Ask your GP to refer you. Any GP seeking to locate a reputable NHS allergy clinic can refer to the handbook issued by the British Society for Allergy and Clinical Immunology (020 8398 9240).
Common causes include foods such as peanuts, tree nuts (e.g. almonds, walnuts, cashews, Brazils), sesame, fish, shellfish, dairy products and eggs. Non-food causes include wasp or bee stings, natural latex (rubber), penicillin or any other drug or injection. In some people, exercise can trigger a severe reaction - either on its own or in combination with other factors such as food or drugs (e.g. aspirin).
Fresh fruit allergy may occur in people who are allergic to pollen. This is frequently mild, but a doctor's advice should be sought.
There is no perfect way to measure an individual's potential for a severe allergic reaction, but, in making a diagnosis, an allergy consultant can do several things that will provide clues. Most importantly, the specialist will take a detailed history of previous reactions and other allergic conditions you may have. Valuable information can also be provided by means of skin prick tests and blood tests (R.A.S.T. or CAP assay).
Common food allergens
Severe allergic reactions (anaphylaxis) can be triggered by a wide range of foods. Theoretically almost any food may be implicated, but by far the most common culprits in the UK are peanuts and tree nuts (such as almonds, Brazils, hazelnuts, cashews and walnuts).
It is sensible to view any allergic reaction to these foods as potentially serious. Even apparently mild symptoms should not be ignored because it is possible that future reactions may be more severe. Medical advice should be sought and the food causing the problem must be avoided.
If peanuts are the problem food, you will need to check ingredient labels thoroughly for items such as:
If you are allergic to almonds, avoid almond essence. Roasting and heat treatment do not reduce the allergenicity of peanuts or tree nuts.
Recipes do sometimes change. Foods most likely to contain peanuts or tree nuts include:
Foods sold in restaurants and other catering outlets, or at in-store bakery and delicatessen counters, are generally unlabelled and so pose a particular problem. It's best to be direct with staff - pointing out the seriousness of the allergy. If staff cannot give a guarantee that a specific dish is safe, it is best to eat elsewhere.
It is fairly common for someone with peanut allergy to react to tree nuts, and vice versa. Even if there are some nuts you can tolerate, there is always the chance of cross-contamination with those you are allergic to. For this reason, doctors will often advise people with peanut or nut allergy to play safe and avoid all nuts.
A research team based in Southampton showed that refined peanut oil poses little or no risk for the vast majority of people with peanut allergy, in contrast to unrefined peanut oil, which is likely to retain its allergenicity. Beware of salad dressings containing unrefined nut oil.
Peanuts (Arachis hypogaea) are actually legumes but it is probably unnecessary to eliminate other legumes (such as peas, beans and lentils) unless there is good reason to suspect they cause problems. An American study found that only five per cent of their selected population of children who reacted to legumes suffered symptoms with multiple legumes.
One legume that people should be cautious about is lupin. Lupin allergy is believed to be rare, but could spread if lupin flour becomes more widely used. People with peanut allergy may be more susceptible than most.
Lupins have a long history of being cultivated for their edible seeds, which can be eaten whole or used to make flour.
There have been several reports in the UK of people with peanut allergy reacting to lupin, and a few dramatic cases have come from the Continent.
In 1999 a French research team investigated the risk of cross-allergy to lupin in 24 people who were allergic to peanuts. They found that 44 per cent reacted positively to a skin prick test with lupin flour and seven out of eight who took oral challenge tests reacted positively. The principal allergen in lupin flour was also found in peanuts.
Sesame allergy is fairly common in some countries, including Australia and Israel, and it would appear to be on the increase in the UK. Occasionally reactions are severe. Even when these are mild or moderate, it must be assumed that a future reaction may be severe and medical advice should be sought in all cases.
The rise in sesame allergy is probably linked to its increased use in cooking: it is often used for flavouring and decorative purposes in foods. People who are allergic to sesame must seek to avoid it completely, as even a tiny amount may trigger a severe reaction.
Dishes containing sesame include: tahini, gomashio, hummus and halvah. Chinese stir fry oils sometimes contain sesame oil. Sometimes it is to be found in Aqua Libra.
People have also reported allergic reactions to vegeburgers, breadsticks, burger baps, cocktail biscuits, Middle Eastern foods, Chinese and Japanese foods, stir fry vegetables and health food snacks containing sesame.
Sesame oil should be regarded as extremely risky because it is almost certain that it will be unrefined, and therefore contain the allergenic proteins that trigger allergic reactions.
Bread and other products bought from in-store bakeries must also be viewed as suspect because these may be contaminated by sesame seeds from other bread.
Sesame is sometimes used in cosmetics and other personal care products and in such cases may be labelled under the Latin name sesamum indicum. Sesame oil may occasionally be present in pharmaceuticals. Always ask your pharmacist to obtain full ingredients of any prescribed medicine.
Allergy to sesame needs to be treated as seriously as peanut allergy. Nevertheless, people affected can be assured that with proper management, the risks will be minimal. Central to any management strategy are proper medical advice, care and vigilance at all times and a commitment by the patient to carry prescribed medication everywhere.
Egg allergy - common among children - is usually mild. But in rare cases egg can trigger anaphylaxis. Food labels must be thoroughly scrutinised for products containing egg or albumen.
The emulsifier known as lecithin can be derived from egg, although in practice this is uncommon. If you in doubt about any product, it is best to contact the retailer or manufacturer.
Some egg-allergic children can eat well-cooked egg (in cake, for example) without any ill effects - but not raw or lightly cooked egg. Others are allergic even to egg which has been well cooked. People who are fine with cooked egg are more likely to grow out of egg allergy.
A lot of fresh pasta contains egg, but you will certainly be able to find a dried pasta that is egg-free. Some varieties may occasionally carry a very small risk of cross-contamination with egg. Check with individual companies to identify the safe ones.
Some supermarkets produce lists of their own-brand products free from egg. Many people find these invaluable.
The MMR injection is normally cultured on egg. Anaphylactic reactions to the MMR have been reported, but they are very rare. In any case, it's possible that in those instances, a component other than egg was responsible. If there are any concerns, the vaccination should be given to the child as an outpatient in a paediatric department with full resuscitation equipment available. Normally a test dose is given before the full dose.
The term cow's milk allergy is generally used to describe reactions generated by the immune system. This is how the term will be used here. Non immune reactions are normally classified as cow's milk intolerance.
Cow's milk allergy is common in infants and very young children. It rarely develops after one year of age and the onset is closely related to the introduction of cow's milk based infant formula. The prevalence is estimated to be as high as two per cent among children under a year old. Fortunately about half outgrow their allergy by one year, and most children have outgrown it by the age of three.
However, cow's milk allergy may occasionally be lifelong and severe.
In early infancy, symptoms are usually tummy pain and vomiting. In a small number of infants there is nettle rash, swelling of the face, eczema and respiratory symptoms including asthma.
As the infant gets older, typical allergic reactions to milk include rash, hives and redness around the mouth, which can spread all over the body, runny nose, sneezing and itchy watery eyes, coughing, choking, gagging, wheezing and trouble breathing, abdominal cramps, vomiting and diarrhoea. The reaction can stop at any stage or develop into anaphylaxis (a serious allergic reaction that affects a number of body organs).
In severe cases, an allergic reaction to milk can develop into anaphylaxis with minute amounts. Strict avoidance of all traces of milk and all its derivatives is the only way to deal with this type of allergy. Some people choose to keep milk products out of the house. Emergency adrenaline (epinephrine) should be prescribed and kept within close proximity at all times.
Small traces of milk products in cooked goods can be eaten without causing a reaction. Lactose is usually tolerated but avoid milk, cream, cheese, yoghurt and ice cream.
Small amounts of processed dairy products (e.g. yoghurt and cheese) can be tolerated. The child is likely to outgrow milk allergy at an early age.
A food does not have to be eaten to cause a reaction, although eating it causes more severe reactions. Hives can occur on skin contact with milk. If food gets into the wet surfaces (e.g. through a cut in the skin, on the lips or in the eye) severe reactions can occur.
The smell of a food, such as the cheese on a pizza, can cause allergic reactions. These are not normally severe unless in extremely high concentrations. Less severe reactions caused by smell tend to cause minor symptoms (e.g. itchy eyes, runny nose and sore throat).
Degrees of avoidance will depend on the individual and the severity of the milk allergy. Many people need to avoid milk and dairy but can cope with trace amounts in cooked goods (e.g. cakes, biscuits and pies).
Milk can be found in many unlikely foods. It is often used in very small quantities in manufactured goods, and so it is affected by the 25 per cent rule governing compound ingredients – which means that manufacturers and retailers are under no legal obligation to include very small amounts in the ingredient list. Fortunately many companies voluntarily declare milk even when they are not compelled to, but ingredient labels always need to be viewed with caution. Many food companies provide lists of products that are milk free.
Thankfully, the 25 per cent rule is likely to be amended under new European legislation and so in due course the problem of undeclared allergens such as milk will be a thing of the past.
Check food labels every time you shop – even if you have bought a product before. Recipes do sometimes change.
Natural flavours and seasoning are terms to watch out for as they can contain milk proteins. They may be labelled only as natural flavouring or seasoning in products like crisps, processed meats, pies, sausages, biscuits and cakes. This is another reason why lists of milk-free products are valuable.
Avoidance and vigilance should also extend to other activities besides eating – particularly where a child has a severe milk allergy. Playtime can be hazardous if other children are putting toys in their mouths. Ice creams melted into sand used for making sandcastles, and ice creams dropped in paddling pools, have also been known to cause problems on rare occasions.
Many medicines contain milk products and lots of tablets are manufactured with the aid of lactose. Lactose does not normally contain the proteins responsible for causing reactions, but could possibly be contaminated with milk protein – therefore people with very severe milk allergy may be wise to avoid anything with lactose in it.
A number of the dry powder asthma inhalers contain lactose although the aerosol ones all seem to be fine. There are currently no antihistamine tablets available in the UK that are free from lactose, so people with severe milk allergy are advised to stick to the syrups i.e.Chlorpheniramine (Piriton), and Loratidine (Clarityn).
Most people with milk allergy find that antihistamines (e.g. Piriton) are usually sufficient to treat their symptoms. However if you have breathing difficulties or anaphylaxis has been diagnosed, then adrenaline (epinephrine) should be carried at all times (e.g. EpiPen or Anapen). These are auto injectors, which are very easy to use and designed for self-administration.
The above list may not be exhaustive. Examples of foods/products which may contain milk. Read ingredient lists carefully and, when in doubt, check with food companies.
There may be delayed gastro-intestinal symptoms, such as vomiting, diarrhoea and colic. These symptoms can develop over hours or days after ingesting a modest amount of cow's milk (over 120mls or 4oz). Delayed responses can produce severe symptoms resembling anaphylaxis, although this is rare. Allergy testing is not effective for milk intolerance. Milk intolerance usually does not cause eczema, hives, or breathing difficulties. Antihistamines do not work either. Strict milk avoidance is not necessary, and traces in baking can be safely eaten.
People who are allergic to milk react to the milk protein and not to the milk sugar (lactose). Lactase deficiency is quite different and caused by the lack of the enzyme lactase, which is needed to digest lactose.
As stated above, it is generally thought that people with milk allergy do not need to avoid lactose because it does not contain the proteins responsible for allergic reactions. However, it is purified from cow's milk and may contain trace amounts of milk proteins. People with severe cow's milk allergy should avoid products containing lactose, but those with less severe symptoms will be able to tolerate the possible small amounts of milk protein in lactose.
Adverse reactions to shellfish are rare in young children, and are usually not seen until the teenage years or adulthood. This may be a reflection of the fact that shellfish is not normally a part of the diet of young children.
Allergy to fish - such as cod and other white fish - may begin in childhood and is likely to be lifelong. Allergies to shellfish or fish are potentially serious and there may be a rapid onset of symptoms. A GP's advice should be sought in all cases and a referral made to see an allergy specialist. Patients known to be at risk may be prescribed auto-injectors containing adrenaline (also known as epinephrine).
Someone who reacts to one type of fish - even if the symptoms are mild - might be advised to play safe and eliminate all fish from their diet. This is partly because they may react to another type of fish, but also because of the high risk of cross-contamination among different types of fish (e.g. at fish markets or on fish counters).
This also applies to shellfish. People allergic to one type of shellfish are often advised to avoid all shellfish.
Biologically speaking, shellfish are aquatic invertebrates rather than fish. They can be divided into four main groups:
People who have reacted to one type of shellfish (e.g. crab) are likely to react to other members of the same group (in this case, other crustaceans). If you react to crab, avoid that and the rest of the crustacean group. If you react to squid, avoid that and the rest of the cephalopod group. Shellfish from the other groups may not necessarily present a problem, although they may do for some people. It is advisable to avoid them anyway. A special reason for being cautious is that there is a relatively high risk of cross-contamination among different types of seafood.
Kosher food is shellfish-free. Always read the labels and check with food companies if you are unsure.
Fish and shellfish are biologically distinct. People who are shellfish-allergic may be able to eat fish, and vice versa - unless they have both allergies. But as stated above, be aware of the risk of cross contamination in restaurants, markets and open fish counters. If the same pair of tongs is used to handle different types of fish and shellfish, or if you suspect one type of fish or shellfish may have spilled over and had contact with another, you should avoid buying or consuming.
People have been known to go into anaphylactic shock after breathing in airborne particles of shellfish or fish allergen in open fish markets.
In restaurants, inform staff of your allergy. Find out what your food is fried in, and whether the oil has been used for anything else. Check the ingredients of all stocks and soups. Ideally, your companions should avoid eating fish/shellfish in your presence, as there is a small risk that breathing in the cooked food may cause a reaction.
As they are relatively expensive, shellfish and fish are rarely an undeclared or unexpected ingredient in pre-packaged foods. Always check the label for the type of shellfish/fish to which you are allergic. Some supermarkets (e.g. Sainsbury's) will have a "CONTAINS" bar, which will indicate the presence of fish and shellfish, but policies vary from store to store and brand to brand. Be vigilant when choosing stocks, soups and highly processed foods, which may contain shellfish or fish extract to add flavour.
Dishes to look out for include paella, bouillabaisse, gumbo (a Tex Mex dish), frito misto (a mixed fried fish dish from the Mediterranean coast), and fruits de mer (seafood). Oriental food tends to contain lots of different kinds of fish at once, and chopped pieces can be difficult to spot.
Surimi (a processed seafood product) is usually made from white fish but may contain shellfish extract. Surimi can be present in processed foods such as pizza toppings.
Caesar salad dressing normally contains anchovies. Worcestershire sauce may.
Caponata, a traditional sweet and sour Sicilian relish, can contain anchovies.
Kedgeree is made with rice and fish.
Fish sauce is a common ingredient in the Far East. Terms to look out for are Nuoc Mam and Nam Pla.
Fish sauce can be made with shellfish as well as fish.
Patum Peperium (Gentleman's Relish) is a spread made with anchovies.
Check the ingredient lists on ready-made Oriental sauces, pastes and prepared meals. In fact check the ingredient lists of all food for unexpected ingredients.
People with shellfish allergy are sometimes warned against iodine, an element present in a wide range of items including shellfish, seaweed, cleaning products, and X-ray dyes. However, iodine allergy is unrelated to shellfish allergy. The allergen present in shellfish is not iodine but muscle protein in the flesh.
Although it is the flesh of shellfish that contains the allergen, people with shellfish allergy are advised to avoid shellfish shells and skeletons. Glucosamine, used in the treatment of arthritis, is derived from the skeletons of shellfish and is unsuitable for people with shellfish allergy. Chondroitin is a shellfish-free alternative. Chitin, derived from shellfish shells, is used in commercial "fat absorbers" such as Chitosan HD, and should be avoided. Moisturisers can also contain shellfish-derived chitin. Some calcium supplements may contain ground oyster shells.
Some people who think they are reacting to seafood are actually having an allergic reaction to a worm-like parasite called Anisakis (also known as the cod worm). This parasite, relatively common in Spain, can cause urticaria, gastrointestinal upset or even anaphylaxis when present in fresh cephalopods, or hake, anchovy or cod. If you react to a particular fish on one occasion, but subsequently eat it with no problem, you should consider the possibility that the cod worm was responsible. Speak to your doctor.
On rare occasions, people who think they react to seafood (or other food for that matter) may be reacting to the latex gloves used in preparation. They should consider the possibility that they may be latex allergic and speak to their doctor.
Adverse reactions to seafood are not always symptomatic of genuine allergy.