Allergic diseases

Question 1

Allergic rhinitis

Answer 1

Common
High morbidity
Aeroallergens: house dust mites, pollens, moulds, animal dander

Inv:

• skin prick test
• specific IgE

Mx;

• avoidance
• antihistamine, intranasal steroids
• desensitisation (subcut immunotherapy - SCIT vs sublingual SLIT)
• omalizumab

Question 2

Omalizumab

Answer 2

Humanised monoclonal anti-IgE antibody

Binds free IgE, dec high-affinity IgE receptor expression on MC

Proven efficacy for

• severe, refractory allergic asthma
• allergic rhinitis

Question 3

Food allergy

Answer 3

Common culprits:
- cow’s milk, egg, wheat, soy, seafood, nuts

Dx:

• Hx
• skin prick test
• specific IgE
• oral food challenge (gold standard)
• novel tests (peptide microarray)

Mx:

• avoidance
• action plan
• immunitherapy

Question 4

Anaphylaxis

Answer 4

Severe acute allergic reaction

Skin/mucosal (though may be absent in up to 20%) AND => of respiratory, hypotension

Dx:

• clinical
• serum tryptase (peaks 60-90 mins, persists up to 5 hours, beware false negatives, may not be elevate with food anaphylaxis)
• plasma histamine (peaks in 5 mins, back to baseline in 1 hour, not helpful!)

Mx:

• acute/emergency mx
• refer to immunologist/allergist, action plan, identify triggers, comorbidities, education, avid triggers, immunomodulation

Question 5

Insect sting/venom anaphylaxis

Answer 5

Dx:

• Hx
• skin prick testing and intradermal testing
• specific IgE (less sensitive than SPT)
• basophil activation test

Mx:

• avoidance
• large local reactions: symptomatic therapy
• systemic reactions: acute - antihistamines, adrenaline; longterm - confirm reaction is systemic, desensitisation

Question 6

Drug allergy

Answer 6

<10% of all adverse drug reactions
Not dose-dependent
Triggered by minute doses of antigen
Clinical presentation similar to other allergic reactions
Effects not explained by pharmacological effects of the drug
Hypersensitivity can be defined by specific tests in vitro or in vivo to demonstrate presence of antibodies

Question 7

In vitro testing

Answer 7

Specific IgE
Total IgE - not helpful

Tryptase - helpful if collected within 3 hours, does not distinguish between IgE and non-IgE mediated causes

Question 8

In vivo testing

Answer 8

Ig-E mediated reactions:

• skin prick testing (identification of specific IfE antibodies, limited by availability of appropriate reagents, valid non-irritative dilutions
• intradermal testing

Non-IgE mediated reactions:
- patch testing

Either:
- drug provocation test (DPT) - to exclude hypersensitivity when Hx not suggestive, to confirm diagnosis when SPT and SpIgE neg