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1 Added by Dr. Mahadev Desai on plexusmd.com, May 2015

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Food Allergy

Dr. Mahadev Desai, MD [email protected]

May, 2015

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www.plexusmd.com • [email protected]


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Disclaimer

This presentation is prepared by leading medical experts solely for academic purposes

and intended for reading only by qualified Medical doctors. The objective is to spread

awareness and make clinical management-related information handy for consultants

across specialties and setups. The reader is advised to use own discretion while

relying upon information provided in this presentation and refer more comprehensive

sources if required in a given set of circumstances. This is not a comprehensive note

on the subject – various information may be concised, abbreviated or curtailed to

highlight only the most important aspects in the author’s opinion. PlexusMD and the

author expressly disclaim any liability arising out of the use of the information

provided here.


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Agenda

• Food allergy vs. Food intolerance

• Common foods causing allergy

• Clinical features

• Diagnosis

• Management


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How common is Food Allergy?

About 5-10 % of children have clinically proven allergic

reactions to foods.

In teens and adults, food allergies occur in about 4% of

total population.

People often have an unpleasant reaction to something they ate and wonder if they have a food allergy.

Being allergic to milk is different from not being able to digest it properly due to lactose intolerance.


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Food allergy vs. Food intolerance

Food Allergy Food Intolerance

Examples:

• Acute: anaphylaxis (IgE-mediated) • Chronic/Recurrent: Celiac disease

(Non-IgE-mediated)

• Lactose intolerance • MSG-headache • Histamine rich foods (cheese, wine, fish) • Migraine headache

• Hypersensitivity reaction to food proteins

• Classically IgE mediated (occasionally non-IgE mediated)

• Dose-independent

• Occurs every time with same food

• Could be life-threatening

• Non-immune mechanisms:

• Toxic, Pharmacological, Metabolic or Psychogenic

• Dose (quantity) - related

• Usually mild to moderate

• Immune-mechanism

• IgG mediated


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Common foods causing allergy

• Milk

• Eggs

• Wheat

• Fish

• Peanuts

• Shellfish

• Soy

• Tree Nuts

Eight foods cause 90% of the allergic reactions, as per data from the US

Children

• Milk, egg, peanuts, wheat, soy, tree nuts (almonds, walnuts)

• Most will outgrow eggs, milk, wheat and soy

Adults

• Peanuts, tree nuts, fish, shellfish (shrimp, lobster, crab), mollusks (oysters, clams, scallops)


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Hidden allergens

• Eggs: baked goods, noodles

• Milk: pies, cheese

• Soy: baked goods, candy

• Wheat: flours, soup mixes, snacks

• Peanut: candy, baked goods, ice cream

• Fish: seafood flavors

Chinese, Indonesian, Mexican, etc dishes usually made with peanuts

Cross-contamination of allergens should also be kept in mind, for e.g. peanut soup may also have tree nuts to

which patient may be allergic


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IgE mediated allergy

Exposure

Sensitization

Symptoms

Genetic Predisposition

Re-exposure


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Approach to a case of food allergy or intolerance

• Detailed history

• Diet diary

• Elimination diet

• Food challenge

• Investigations:

• Blood tests

• Skin prick tests

• Biopsy


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IgE mediated allergy - Management

• Rapid onset, typically beginning within minutes to two hours from the time of ingestion

• Vomiting, diarrhea, abdominal cramps and bloating

• Pruritus, swelling of lips & face

• Breathlessness, choking sensation

Signs and symptoms

Examination findings

Management: Treat as

Anaphylaxis

• Cold skin, cyanosis, tachycardia, hypotension

• Bronchospasm, cardiac arrhythmia, cardiac arrest

• Dermographism

• Inj. Adrenaline, IV fluids (if hypotension)

• Inj. Hydrocortisone

• Inj. Antihistaminics (H1 & H2 antagonists)

• O2, Nebulized Salbutamol, Ipratropium

• Inj. Theophylline


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Prevention is the cure

If you are known to be allergic to certain foods:

• Prevention is the cure – do not consume the allergic foods

• Read the ingredient list on all food items

• When traveling, carry special foods

• When eating out, ask about foods with common allergens

Care in children

• Don’t introduce solid foods too early – wait about 6 mths

• Wait on foods with common allergens Cow milk – age 1 Eggs – age 2 Peanuts, nuts or fish – age 3 or after

- American Academy of Pediatricians


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Food allergen labeling and Consumer Protection Act

• Food labels must declare major food allergen in plain language: milk, egg, peanut, tree nuts, wheat, soy, fish and shellfish

• Either in the ingredient list by either of these two methods:

“Contains” followed by allergen; for e.g. Contains: milk and wheat

Parenthetical statement in the list of ingredients; for e.g. albumin (egg)

Read the label carefully for ingredients


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Food-related auto-immunity: Celiac disease

Celiac disease, celiac sprue or gluten-sensitive enteropathy

Wheat, barley, rye contain Gluten (which contains Gliadin) – a type of protein

Gliadin interacts with a specific genetic form of HLA receptor within intestinal

mucosa/submucosal layer causing an inflammatory reaction

Leads to truncating of villi lining the small intestine (villous atrophy)

Causes interference with absorption of nutrients


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Celiac disease – clinical manifestations

• Diarrhoea, weight loss, abdominal pain

• Chronic fatigue, weakness, malnutrition

• Osteoporosis, arthritis and joint pain

• Anaemia

• Infertility, frequent miscarriage

• Depression, behavioural changes

In children:

• Failure to thrive

• Irritability

• Diarrhoea and bloating


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Celiac disease – Diagnosis

• Anti-tissue transglutaminase (tTG) – IgA and IgG antibodies

• IgA endomysial antibody

• IgG or IgA deamidated Gliadin Peptides (DGPs)

• Quantitative IgA (5% have IgA deficiency)

Celiac disease occurs in genetically susceptible individuals with

presence of HLA-DQ2 (90-95%) or HLA-DQ8 (5%)

Absence has high negative predictive value

Screening for Celiac disease

National Institute for Health and Clinical Excellence (NICE), UK recommends screening for celiac disease in people with:

• Newly diagnosed chronic fatigue syndrome

• Irritable bowel syndrome

• Type 1 diabetics, especially those with insufficient weight gain or

unexplained weight loss


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Celiac disease – Management

• Life-long gluten-free diet

• Wheat and wheat products

• Barley

• Rye

• Rice, Milk, Fruits, Vegetables do not contain gluten

About the Author:

Dr. Desai, an Editorial Board Member at PlexusMD, is a senior Physician with over 30 years of teaching experience. He has been the Editor of Gujarat Medical Journal and chaired numerous Scientific sessions. He is currently HOD of Medicine at Ahmedabad Dental College.

Dr. Mahadev T. Desai, MD Consultant Physician Ahmedabad Connect at: plexusmd.com/drmahadevdesai

Thank You

https://plexusmd.com/drmahadevdesai

https://plexusmd.com/drmahadevdesai

Primer is an initiative by PlexusMD to present interesting, important and useful topics in a 10-minute read. Leading experts across the country prepare 15-20 slide primers with a strong emphasis on practical aspects of diagnosis and management. Presentations are authored by members of our Editorial Board and active PlexusMD users and are based on a lot of research and experience.

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