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Asthma and Allergy. Atopy v Allergy Asthma Aeroallergens – indoor & outdoor Occupational allergens. Atopy. The propensity to produce IgE to allergens Demonstrated using Skin prick tests to common inhalant allergens. Allergen-Antibody interaction. Prick Test Reagents. Skin Prick Tests.
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Asthma and Allergy • Atopy v Allergy • Asthma • Aeroallergens – indoor & outdoor • Occupational allergens
Atopy • The propensity to produce IgE to allergens • Demonstrated using Skin prick tests to common inhalant allergens
Allergy • IgE mediated inflammatory tissue damage in response to an allergen causing clinical disease
Asthma - epidemiology • X 2- 3 increase last 30 years • Concomitant similar increase in atopy, hayfever and eczema • ? Environmental Change • ? Less infections ( hygiene hypothesis )
Allergens • Outdoor • Pollens- • Tree • Grass • Moulds- • Alternaria • Aspergillus • Cladosporium • Penicillium
Allergens • Indoor • Cat • Dog • Cockroach • Birds
Inhalation of allergen • Immediate response ( IgE mediated ) • Max: 20 min. • Ends : 60 min. • Late response in 50% (Eosinophil ) • Onset 3h • Max 12 h • End 24 h • Responsible for airways hyperreactivity • Allergen ID and avoidance therefore very important
Allergic history and negative skin tests • Remember grass pollen allergy
Pollenosis • Prof. Paul Potter, Cape Town • Big role for grass pollens in respiratory allergy • Kikuyu grass • Bermuda grass • Buffalo grass ( l’herbe bourrique ) • SPT regents to detect allergy to these being developed • Mauritus has all of these grasses in abundance
Why study pollens • Potential for immunotherapy
Indoor allergens-avoidance • House dust mite allergen • Large • Not easily air-borne • Needs close proximity to bedding to be inhaled
House dust mite avoidance • Mite impermeable mattress covers • Hot wash bedding linen ( 55 C ) • Remove moquettes • Light curtains • Vacuum clean with high filtration cleaner
Pet allergens • Remove the pet • Clean it • Remove carpets ( x 100 fold antigen)
Asthma- none of usual aeroallergens Think of occupational asthma
Occupational Asthma • Asthma initiatedby an agent inhaled at work • Cf. Work-related asthma • Pre-existing asthma provoked by an irritant in the workplace
Occupational asthma • Only a % of workers affected • Latent period before onset ( 2 Yr.) • Improvement during periods away from work • Once established can be triggered by really small doses of antigen
HMW ( Biologic ) Latex Flour ( 334 ) Laboratory mammals(188) Bacillus subtilis LMW ( haptens ) Colophony ( 175 ) Wood dust Diisocyanates ( 658 ) Platinum salts Acid anhydrides ( 364 ) Glutaraldehyde Plastics workers Bone cement Usual suspects
Occupational asthma • Diagnosis will have major impact on patient’s life • False + ve : needless loss of job • False – ve : Needless continuing exposure • Be careful
Thank You • Discussion