Shellfish are often blamed for causing an “upset stomach,” and the assumption may be that it is caused by a “shellfish allergy.” This may indeed be the case because shellfish are one of the commonest causes of allergy and in some cases reactions can be severe. Any significant reaction to shellfish should be investigated by appropriate allergy testing and on no account should someone who suspects that a reaction was due to allergy, try a home “challenge” in case the most severe type of allergic reaction known as “anaphylaxis” is induced. Such challenges, if necessary at all, should only be done in a hospital setting by someone trained in diagnosing and managing severe allergic reactions.

However, not all shellfish reactions are allergic in nature. This paper describes other causes of reactions that may be confused with allergy.

NOT ALL SHELLFISH “ALLERGY” IS ALLERGY

COUNTRY : USA

ABSTRACT
The popularity of shellfish has been increasing worldwide, with a consequent increase in adverse reactions that can be allergic or toxic. The approximate prevalence of shellfish allergy is estimated at 0.5-2.5% of the general population, depending on degree of consumption by age and geographic regions. The manifestations of shellfish allergy vary widely, but it tends to be more severe than most other food allergens.

Tropomyosin is the major allergen and is responsible for cross-reactivity between members of the shellfish family, particularly among the crustacea. Newly described allergens and subtle differences in the structures of tropomyosin between different species of shellfish could account for the discrepancy between in vitro cross-antigenicity and clinical cross-allergenicity. The diagnosis requires a thorough medical history supported by skin testing or measurement of specific IgE level, and confirmed by appropriate oral challenge testing unless the reaction was life-threatening.

Management of shellfish allergy is basically strict elimination, which in highly allergic subjects may include avoidance of touching or smelling and the availability of self-administered epinephrine. Specific immunotherapy is not currently available and requires the development of safe and effective protocols.

But symptoms after consuming shellfish may be due to something else:

Shellfish poisoning frequently masquerade as an allergic reaction. Ingestion of contaminated shellfish results in a wide variety of symptoms depending on the concentration of toxins and amount consumed. Five types of shellfish poisoning have been identified [9]. Scombroid poisoning [10] has been linked to fish by the action of bacteria on muscle histidine and production of histamine. To the best of our knowledge, we did not encounter any reports in the English literature on scombroid poisoning from shellfish consumption.

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The National Institute for Health and Clinical Excellence (NICE) has just released a series of documents on food allergy. They concern the diagnosis and assessment of food allergy in children and young people in primary care and community settings. The documents aim to give guidance for those up to the age of 19 years. They reiterate the importance of primary care practitioners to go through the intitial assessment as all doctors are trained to do, of full history taking, physical examination, making a differential diagnosis leading on to a definitive diagnosis.

Where there is any doubt about the diagnosis, the patient has experienced anaphylaxis or other severe reaction, or where there is a need for several or important foods to be eliminated, the advice is to consider referral to an allergy specialist.

There are several documents available on the NICE website. These cover the diagnosis and assessment of food allergy in children and young people in primary care and community settings, a quick reference guide, Information for people who use NHS services, a powerpoint presentation on the subject, cost effective analysis for testing for IgE mediated food allergy, an appendix indicating why some work has been excluded, and a paper describing the scope, review protocol, literature search & search strategies and evidence tables.

The document below is intended for those managing young people with food allergies:

FOOD ALLERGY IN CHILDREN AND YOUNG PEOPLE – Diagnosis and assessment of food allergy in children and young people in primary care and community settings

COUNTRY : UK

“Referral to secondary or specialist care
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Based on the allergy-focused clinical history, consider referral to secondary or specialist care in any of the following circumstances.
- The child or young person has: faltering growth in combination with one or more of the gastrointestinal symptoms described in recommendation
- not responded to a single-allergen elimination diet
- had one or more acute systemic reactions
- had one or more severe delayed reactions
- confirmed IgE-mediated food allergy and concurrent asthma significant atopic eczema where multiple or cross-reactive food allergies are suspected by the parent or carer.
There is:
-persisting parental suspicion of food allergy (especially in children or young people with difficult or perplexing symptoms) despite a lack of supporting history
- strong clinical suspicion of IgE-mediated food allergy but allergy test results are negative clinical suspicion of multiple food allergies.

Alternative diagnostic tools
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Do not use the following alternative diagnostic tests in the diagnosis of food allergy:
vega test
applied kinesiology
hair analysis.

Do not use serum-specific IgG testing in the diagnosis of food allergy.”

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The National Institute for Health and Clinical Excellence (NICE) Have just released a document on food allergy. It concerns the diagnosis and assessment of food allergy in children and young people in primary care and community settings. The document gives guidance for those up to the age of 19 years. It reiterates the importance of primary care practitioners to go through the intitial assessment as all doctors are trained to do of full history taking, physical examination, making a differential diagnosis leading on to a definitive diagnosis.

Where there is any doubt about the diagnosis, the patient has experienced anaphylaxis or other severe reaction, or where there is a need for several or important foods to be eliminated, the advice is to consider referral to an allergy specialist.

TESTING FOR FOOD ALLERGY IN CHILDREN AND YOUNG PEOPLE – Information for people who use NHS services

COUNTRY : UK

“This booklet is about what a healthcare professional should look for when deciding whether to offer a child or young person tests for food allergy, and the steps to follow when making a diagnosis in the NHS in England and Wales. It explains guidance (advice) from NICE (the National Institute for Health and Clinical Excellence). It is written for parents and carers. However, it is recognised that many children and young people will want to know for themselves what the NICE guidance says. This booklet may be useful for them and for anyone with an interest in food allergy in children and young people.
The booklet is to help you understand how food allergy should be diagnosed in children and young people in the NHS. It does not describe food allergy or the tests or treatments for it in detail. Your child’s healthcare professional should discuss these with you and your child. There are examples of questions you could ask throughout this booklet to help you with this.”

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It is difficult to sort out the wheat from the chaff in the internet. This is particularly true of websites dealing with allergy, one of the commonest medical conditions that has been increasing in prevalence in recent years.

Those searching the internet for allergy information should be very aware that allergy, because it is so common, is big, big business. The allergy sharks infest the water when there is money to be made.

Today, the BBC are issuing a warning regarding “alternative” allergy tests.

ALTERNATIVE ALLERGY TEST OFFERS “MISLEAD PARENTS”

COUNTRY : UK

“There is no scientific evidence that complementary therapies or kits sold through websites can identify allergies, the NHS watchdog NICE says.

It says sites for services such as hair analysis use plausible stories but are not backed up by scientific evidence.”

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