Tag Archives: food

Prevention of peanut allergy

Use of peanut oil in eczema creams had OR 8 for peanut allergy but retrospective.

Filaggrin deficiency has OR 5 for food allergy, only 3 for eczema!

So could skin protection before early weaning prevent food allergy? Preliminary studies suggest 35- 50% response.

Jewish children in the UK have a prevalence of peanut allergy that is 10-fold higher than that of Jewish children in Israel. This difference is not accounted for by differences in atopy, social class, genetic background, or peanut allergenicity. Israeli infants consume peanut in high quantities in the first year of life, Bamba (peanut snack, like a Wotsit) often used for weaning, so most infants have been exposed by age 12 months. [Du Toit  J Allergy Clin Immunol. 2008 Nov;122(5):984-9]Bamba peanut snack

Gideon Lack at Evangelina hospital in London did LEAP study (Learning about Peanut Allergy), randomized infants with severe eczema and/or egg allergy to receive either no peanut until age 3yr, else an age-appropriate peanut snack (Bamba or smooth peanut butter, 6g) three times a week.   Among the 530 infants in the intention-to-treat population who initially had negative results on the skin-prick test, the prevalence of peanut allergy at 60 months of age was 13.7% in the avoidance group and 1.9% in the consumption group (86% reduction, P<0.001). 98 participants had baseline positive SPT results, only 12% had a positive challenge so most continued the protocol.  Another 10% with SPT>4mm were excluded from the start.

Adherence to the diet was excellent.  Dust samples were taken from some participants’ beds, peanut levels were significantly higher for kids in consumption group.  There was a higher rate of urticaria in the consumption group.

IgE greater than 10 in peanut avoiding group had 100% PPV for allergy.  Peanut-specific IgG4 antibody seems to be linked to tolerance – it went up more in the consumption group, and IgG4:IgE ratio was generally lower in allergic group (most had IgG4 under 1000). [NEJM 2015; DOI: 10.1056/NEJMoa1414850]  See also LEAP-On study, which is the follow up at 72 months, still significant difference.

Michael Perkins’ EAT study of early introduction of 6 common allergens in non-high risk babies showed if strict adherence to protocol eg 2g weekly of peanut, then every case of peanut allergy could be prevented.




Advisory labels

Or precautionary allergy labelling.

What are Precautionary allergy labels?

These are extra bits of information sometimes provided on labels, in addition to the actual ingredients.  Phrases like “May contain…”, “Made in a factory where…”.  These precautionary allergy labels are not legally required, but manufacturers are encouraged to use them to warn their customers of a risk of accidental contamination during the production process.  The Food Standards Agency  (FSA) (2006) encourages manufacturers to be as precise as possible eg which specific nut, or else peanut or “tree nuts” rather than just “nuts” but in reality different companies do different things eg Kelloggs does not differentiate between peanut and tree nuts when they put a warning label on about nuts.

Is there a real risk or not?

Contamination of chocolate is a particular problem, particularly with nuts, and with milk in the case of dark chocolate.  In some studies, half of all the chocolate tested was contaminated.

But most foods carrying such a label will not contain any of the allergen mentioned, indeed it is sometimes hard to imagine how it possibly could!  In an Irish study looking at foods labelled marked “may contain peanut/nut”, 5% had detectable peanut or nut, which is a significant proportion but actually the peanut or nut was present at such low levels they would be unlikely to cause a reaction in the majority of allergic people.

Aren’t they just a way of avoiding legal liability?

The FSA clearly state that these labels should only be used where there is a real and unavoidable risk.  And in any case, it’s not clear it changes the company’s legal responsibilities – if there is evidence that a manufacturer has been producing food in an unsafe manner, they would be liable regardless of whether there was a warning or not.

When is a trace not a trace?

The idea of threshold is important – how much of the allergen is actually present, and is it even enough to cause a reaction?  Not everyone reacts at the same threshold, and the differences between individuals can be a factor of ten or even a hundred.

In big study of peanut challenges in kids, those who got through to last stage were 13x more likely to have anaphylaxis (related to total amount of peanut consumed, presumably). Higher thresholds found in older kids, perhaps because they would have presented earlier if they had lower threshold? [PAI 2018 vol 29:754-761]

Australia and New Zealand ask manufacturers to look at actual levels of contamination before putting a warning on their products.

In the UK and Europe, the risk associated with the processes is what matters, rather than the actual levels of contamination. It’s not clear which is actually more useful.

So what should you do about traces?

Many people tend to ignore these warnings, particularly when it is something they have eaten many times before, or when it is a big brand name, and when the wording is ambiguous rather than direct.  Yet there is no good evidence that any of these things actually makes a difference to the real risk.

What is definitely true is that people have unexpected reactions and this can be after eating things marked with these warnings, but equally after eating things without these warnings.

What is also true is that allowing yourself to eat things marked with these warnings makes life much simpler!

Some patient organizations eg Anaphylaxis Campaign recommend avoiding anything marked with precautionary allergy labels, if only because this puts the control in your hands rather than leaving you at the mercy of the manufacturers.

Doctors often recommend avoiding anything with an allergy warning, because it “seems” safer and they don’t appreciate how difficult it is in day to day life.

So I think you have to make your own choice.  If you have a nut allergy, and it’s chocolate or something else that often does contain nuts eg a muesli bar, then to me the risk seems too much.  It it’s something that wouldn’t usually contain nuts, and you’ve had it before, and you’re at home with your family, then maybe the risk is acceptable to you.  But if you are away on holiday, and you’ve forgotten to bring your allergy medicines, and your asthma is playing up, and it’s late at night, then that’s probably the worst time to take a chance.    


Food allergy labelling

The UK still currently follows the European Food Information For Consumers Regulation (FIR) that took effect from December 2014.

This applies to unpackaged food eg restaurants, takeaway’s deli’s, bakeries etc. It now also applies to food prepacked for direct sale (PPDS) such as a sandwich made on the premises of a cafe but wrapped (Natasha’s law).

Allergy advice boxes are no longer permitted, although “may contain” advisory labels are. The allergen should be emphasised in the ingredients panel through typeset eg font, style, colour.   The specific type of cereal or nut must also be stated.

The 14 allergens that must be highlighted under UK/European law are: cereals containing gluten (wheat, barley, rye etc), crustaceans (eg shrimp, prawn), molluscs (eg mussel, oyster), eggs, fish, peanuts, nuts, soybeans, milk, celery, mustard, sesame, lupin and sulphur dioxide at levels above 10mg/kg, or 10 mg/litre, expressed as SO2. Lupin and Molluscs added later.

There are some exceptions, where the food is so highly processed that they are no longer capable of triggering an adverse reaction eg fish gelatine in beer/wine, soya in vegetable oil.

If your allergy is not one of those listed, eg lentil, there is no legal duty for the manufacturer to highlight the presence of that ingredient, or for the restaurant to provide a full list of ingredients.  So you need to read the full list of ingredients carefully, and plead with the restaurant for details relevant to your allergy. In the past, some manufacturers highlighted allergens in a separate box, but this is no longer permitted.

The rules list nuts as:

  • almond,
  • hazelnut,
  • walnut,
  • cashew nut,
  • pecan nut,
  • Brazil nut,
  • pistachio nut,
  • macadamia nut or Queensland nut
  • and products made from these nuts.

Other types of nuts, and other foods which are not nuts (even though they are called nuts i.e. chestnuts, pine nuts and coconut), are not named in the rules, even though they are known to cause allergy in some people.

Note that by law, “cereals containing gluten” includes oats! Spelt and Kamut should be declared as containing wheat. Oats contain avenin, rather than gliadin, but related. Products containing oats that have not been contaminated by wheat can be declared “gluten free” by law, so effectively the law considers oats as both containing but not containing gluten…

See also Advisory labels.

(food.gov technical guidance on new labelling law)

There is no legal duty to highlight changes in recipes on packaging.  The same product with the same packaging can sometimes have different ingredients, depending on where it is produced.

The Food Standards Agency (FSA) has ordered councils to encourage restaurant owners to check their ingredients.

Note that non-EU countries will have their own rules eg US has only 10 ingredients that must be highlighted (not molluscs, mustard, celery, or lupin).

Scombroid Poisoning

Differential diagnosis to allergy. Basically Histamine poisoning, rather than release of endogenous stores! Mild examples are not uncommon but severe cases rare. Clue is that several people who eat the same seafood meal fall ill with similar allergic symptoms!

Histamine and other amines are produced by bacteria from certain amino acids (can occur during production eg Swiss cheese or by spoilage). Particularly affects fish of the Scombridae family (viz tuna, mahi mahi, bluefish, sardines, mackerel, amberjack, and abalone) but can be any food containing the right amino acids and subject to the right bacterial enzymes.

Fish/shellfish allergy

Seafood as a term includes fish and shellfish.  But allergy to one does not imply allergy to the other! In fact, shellfish allergy is linked strongly to house dust mite allergy rather than fish, probably since they are all invetebrates with the same sort of Tropomysins.  Co-sensitivity is relatively common (20-40% of fish allergic also allergic to shellfish) so must simply be atopic disposition!

Chordata (finned fish) subdivide roughly into bottom feeders, mackerel/tuna [perciformes] group, salmon/trout [salmoniformes] group and the rest (so called “bony fish”).  The best studied allergen Gad c 1, found in cod, is a parvalbumin.  These are found in muscle, esp slow twitch white flesh (cf dark muscled, fast fish eg tuna, swordfish).    50% of those with allergy to one type of  fish will be allergic to another; the rate is higher in shellfish since there is less variation in tropomysins.

Shellfish (crustaceans) are related to molluscs including abalone, clam, mussel, squid, octopus.  Allergy to these is more common in countries where these are commonly eaten viz Spain, Japan.

Sneaky places you find seafood:

  • Soups eg bouillabaisse
  • Pate
  • Seafood “crab” sticks – usually fish, not crab!
  • Worcestershire sauce (anchovy)
  • Pizza (anchovy)
  • Caesar salad (anchovy)

Reactions to seafood may not be allergic:

  • Anisakis is fish parasite, worldwide distribution, with a range of different allergens.  Larvae can cause immediate allergic response, but infection can also produce inflammatory symptoms of varying kinds, depending on where in the digestive tract the larvae are deposited.
  • Scombroid toxicity esp associated with salmon, tuna, mackerel.  Besides flushing, vomiting and wheezing, there can be severe headache and dizziness.  Onset is minutes to hours.
  • Ciguatoxin poisoning associated with reef fish eg sea bass, snapper.  Onset is slower – 30 minutes to hours, besides cramps, D+V there can be myalgia and paraesthesiae.
  • Shellfish (mostly bivalves) can be the source of a range of toxins with effects as diverse as paraesthesia, myalgia, ataxia, even seizures.   Mostly D+V though.

Cod IgE >20 gives 95% PPV, other cut offs lacking.  Given importance of omega 3, unnecessary restriction should be avoided – Canning fish reduces immunogenicity, challenge?  Interestingly, many fish allergens seem to get MORE allergenic with heating, not less – Gad c 1 is known to become airborne in steam without denaturing! Various cases of fatal anaphylaxis simply to inhaling vapour of frying fish (aerosolised proteins, NOT smell, that causes reaction).