Allergies

Question 1

What may an abnormal immune system result in?

Answer 1

Allergic diseases
Immune deficiencies
Autoimmune disorders

Question 2

What is meant by hypersensitivity?

Answer 2

Objectively reproducible symptoms or signs following exposure to a defined stimulus at a dose usually tolerated by most people.

Question 3

What is meant by allergy?

Answer 3

Hypersensitivity reaction initiated by specific immunological mechanisms. It can be IgE mediated (peanut) or non IgE mediated (codliac)

Question 4

What is atopy?

Answer 4

A personal and/of familial tendency to produce IgE antibodies in response to ordinary exposures to potential allergens, usually proteins.

Associated with asthma, allergic rhinitis, conjunctivitis, eczema, food allergy.

Question 5

What is meant by anaphylaxis?

Answer 5

A serious allergic reaction with bronchial, laryngeal or cardiovascular involvement.
Rapid in onset and may cause death.

Question 6

Developing immune system must be sensitised to an allergen before an allergic immune response develops. Why is this not always obvious?

Answer 6

Sensitisation can be occult ie: sensitisation to peanut from exposure to trace quantities of peanut in house dust.

Question 7

Allergic immune responses are classified as IgE mediated or non IgE mediated. What are the characteristic features of IgE mediated allergic reactions?

Answer 7

Early phase- this occurs within minutes of exposure to the allergen, it is caused by the release of histamine and other mediators from mast cells.

The early phase causes urticaria, angioedema, sneezing, vomiting, bronchospasm +/- shock.

Late phase response after 4-6 hours, this causes nasal congestion in the upper airway and cough and bronchospasm in the lower airway.

Question 8

What may you find on examination of a child with allergic disease?

Answer 8

Habitual Mouth breathing
Allergic salute (from rubbing nose)
These two make up the allergic facies
Pale and swollen inferior nasal turbinates
Hyper inflated chest or Harrison sulci from chronic under treated asthma
Atopic eczema affecting the limb flexures
Allergic conjunctivitis may also be prominent creases and blue grey discolouration below the lower eyelids

Question 9

What is a food allergy?

Answer 9

When a pathological immune response is mounted against a specific food protein.

Question 10

What are the clinical features of an acute allergic reaction?

Answer 10

Mild reaction:
Urticaria and itchy skin
Facial swelling

Severe reaction: 
Wheeze
Stridor 
Abdo pain 
Vomiting 
Diarrhoea 
Shock 
Collapse 

This reaction would be IgE mediated.

Question 11

What are the clinical features of a non IgE mediated cows milk allergy?

Answer 11

Loose stools and faltering growth

Elimination of the allergy would lead to symptoms dissapearing

Question 12

What clinical features would suggest a non allergic food hyperensitivity?

Answer 12

Vomiting and diarrhoea
Vomiting settles but watery stools continue for several weeks
Stool sample will be positive for reducing substances.

Question 13

How do you diagnose food allergy?

Answer 13

For IgE mediated the most helpful are skin prick and measurement of specific IgE antibodies in blood.

Non IgE rely on clinical history and examination. If indicated, endoscopy and intestinal biopsy may be obtained. The diagnosis is supported by eosinophilic infiltrates.

For both IgE and non IgE mediated food allergies, the gold standard investigation in cases of doubt is exclusion of the relevant food under a dietitians supervision, followed by a double blind placebo controlled food challenge.

Question 14

What are the two types of eczema?

Answer 14

Can either be atopic (evidence of IgE antibodies to common allergens) or non atopic. Atopic eczema is classified as an allergic disease.

Question 15

What has been identified as the key genetic risk factor for eczema?

Answer 15

Filaggrin gene mutation

Question 16

What treatment can be given for allergic rhinoconjunctivitis?

Answer 16

Second generation non sedating antihistamines
Topical corticosteroid nasal or eye preparations
LTRA
Nasal decongestants
Allergen immunotherapy
Systemic corticosteroids

Question 17

What does urticaria present as

Answer 17

Hives and redness, resulting from local vasodilation and increased permeability of capillaries and venules, these changes are dependent on the activatjon of mast cells.

Question 18

What does acute urticaria usually result from?

Answer 18

Viral infection (rash lasting for days) or allergen exposure (rash lasting for hours).

Question 19

How do you treat urticaria?

Answer 19

Second generation non sedating antihistamines which may need to be increased up to four times the standard dose,
In refractory cases, leukotriene receptor antagonists or anti IgE antibody (omalizumab) are helpful.

Question 20

What is a type 1 hypersensitivity reaction?

Answer 20

IgE antibodies to a specific allergen trigger mast cells and basophils to release histamine and cytokines, this causes an IMMEDIATE reaction.

Question 21

What is type 2 hypersensitivity reaction?

Answer 21

This involves IgM and IgG antibodies which trigger the complement system and lead to direct damage of local cells.

Question 22

What is an example of a type 2 hypersensitivity reaction?

Answer 22

Haemolytic disease of the newborn

Transusion reaction

Question 23

What is a type 3 hypernsensitivity reaction?

Answer 23

This involves immune complexes which accumulate and cause damage to local tissues- Autoimmune conditions like RA and SLE

Question 24

What is type 4 hypersensitivity?

Answer 24

This is cell mediated hypersensitivity caused by T lymphocytes. T cells are inappropriately activated and cause damage and inflammation to local tissues- organ transplant rejection and contact dermatitis.

Question 25

What should you ask if you are suspecting a child has an allergy?

Answer 25

Timing after the exposure to the allergen Previous and subsequent exposure to the allergen Symptoms of rash, swelling, breathing difficulties, wheeze and cough Previous personal and family history of atopic conditions and allergies

Question 26

How do you diagnose allergies?

Answer 26

There are 3 main ways: . Skin prick testing . RAST testing . Food challenge testing Skin prick and RAST testing assess sensitisation and not allergy.

Question 27

What is immunotherapy?

Answer 27

In certain cases, specialist centres may initiate a lengthy process of gradually exposing the patients to allergens over months with the aim of reducing their reaction to certain foods or allergens.

Question 28

What can be given following exposure to an allergen?

Answer 28

Antihistamines and steroids which work by dampening the immune response to allergens. Close moniororing IM adrenaline in anaphylaxis

Question 29

What is anaphylaxis?

Answer 29

Life threatening medical emergency which is caused by type 1 hypersensitivity reaction. IgE stimulates mast cells to rapidly release histamine and other pro inflammatory chemicals (mast cell degranulation).

Question 30

What differentiates anaphylaxis from a non anaphylactic allergic reaction?

Answer 30

With anaphylaxis you will get a compromise of the airway, breathing or circulation.

Question 31

What is the presentation of anaphylaxis?

Answer 31

``` History of exposure to an allergen Rapid onset of allergic symptoms- urticuria, itching, abdominal pain, angio oedema SOB Wheezing Swelling of larynx- stridor Tachycardia Lightheadedness Collapse ```

Question 32

What are the principles of managing anaphylaxis?

Answer 32

ABCDE approach Airway- secure airway Breathing- give O2 if required C- IV bolus of fluid if required D- lie the patient flat as this improves cerebral perfusion E- exposure looking for flushing, urticaria and angio oedema Once diagnosis is established then give IM adrenalin, repeat after 5 mins if required Antihistamines such as: oral chlorphenamine or cetirizine Steroids- hydrocortisone You need to measure the serum mast cell tryptase within 6 hours of the event, it stays in the blood for 6 hours before gradually disappearing.

Question 33

What is allergic rhinitis?

Answer 33

Condition caused by IgE mediated type 1 hypersensitivity reaction Environmental allergens cause an allergic inflammatory response to the nasal mucosa It is very common and can significantly affect sleep, mood, hobbies, work and school performance and quality of life.

Question 34

How would allergic rhinitis present?

Answer 34

Runny, blocked and itchy nose Sneezing Itchy, red and swollen eyes

Question 35

What is the management of allergic rhinitis?

Answer 35

``` Avoid trigger Hoover and change pillows regularly, allow good ventilation of the home Oral antihistamines Nasal corticosteroid speays Nasal antihistamines ```

Question 36

What is cows milk protein allergy?

Answer 36

Hypersensitivity to the protein in cows milk, it may be IgE mediated and occur immediately or it may be non IgE mediated, with reactions occuring slowly over several days.

Question 37

What is the presentation of cows milk allergy?

Answer 37

It usually occurs in infants who are under 1 years old, often when they are being weaned and have started on formula milk, however it can occur from breast milk if the mothers are consuming dairy products.

Question 38

What are the symptoms of cows milk protein allergy?

Answer 38

Vomiting Diarrhoea Bloating Abdo pain General allergic symptoms- urticarial rash, angio oedema, cough or wheeze, sneezing, watery eyes and eczema. FAILURE TO THRIVE

Question 39

How do you manage cows milk protein allergy?

Answer 39

Diagnosis is based on full history and examination Skin prick testing can be used but is not always necessary If the mother is breast feeding then she should stop consuming dairy products If the baby is having formula then it should be replaced by hydrolysed formulas (the proteins have been broken down so they no longer trigger an immune response) In severe cases infants may require elemental formulas made of basic amino acids (neocate)

Question 40

What is the difference between cows milk intolerence and cows milk allergy?

Answer 40

Similar GI symptoms however allergy involves the immune system and therefore you get allergic features (rash, angio oedema, cough, sneezing) Infants with cows milk allergy wont be able to tolerate cows milk at all, whereas if they are intolerant they can still tolerate it and will be able to continue to grow and develop but will suffer with GI symptoms while having cows milk.

Question 41

How would you manage cows milk intolerance?

Answer 41

Infants with cows milk intolerance will grow out of it by 2-3 years They can be fed with breast milk, hydrolysed formulas and weaned to foods that do not contain cows milk. After one year of age they can be started on the milk ladder.