Allergy Flashcards
What is an allergy?
An adverse health effect that is due to a specific immune response and occurs reproducibly upon expose to the culprit antigen.
It is a hypersensitivity reaction that can be IgE mediated or non IgE mediated.
What are the 2 key requirements for allergy diagnosis?
Involvement of the immune system
Symptoms to occur with each exposure
What is atopy?
A personal and/ or familial tendency to produce IgE antibodies in response to ordinary exposures to potential allergens, usually proteins
- strongly associated with asthma, rhinitis, conjunctivitis, eczema, food allergy
What is hypersensitivity?
It means that the immune system has reacted in such a way as to cause damage. The signs and symptoms are reproducible when exposed to the specific stimulus.
In clinical practice, allergy manifests in the form of various different conditions such as…
Anaphylaxis Urticaria Angioedema Allergic asthma Allergic rhinoconjunctivitis Atopic dermatitis (eczema) Food and drug hypersensitivity reactions
Can allergy affect every organ?
Yes - although skin and mucous membranes are most commonly involved
The developing immune system must be… to an allergen before an allergic immune response develops.
Sensitised
What is an example of occult sensitisation?
Sensitisation to egg from exposure to trace quantities in maternal breast milk
Only a few stimuli account for most allergic diseases. What are they?
Inhaled allergens: plant pollen, house dust mites, moulds, pet dander
Ingested allergens: cows milk, nuts, soya, egg, wheat, legumes, seafood, fruits
Insect tings/bites, drugs, natural rubber latex
In the UK, what percentage of children have allergic rhinitis, eczema or asthma?
Up to 40%
What percentage of children in the UK develop a food allergy?
Up to 6%
Is the prevalence of allergy increasing or decreasing worldwide?
Increasing
Are allergic diseases the commonest chronic diseases of childhood?
Yes and the commonest cause of school absence and acute hospital admission
What is the hygiene hypothesis?
Proposes that the increased prevalence of allergic diseases is due to altered microbial exposure associated with modern living conditions.
Children exposed to animals and microbes in the early post natal period appear to be protected against certain allergic diseases.
Under the hygiene hypothesis, what factors reduce the risk of allergy or autoimmune diseases?
Developing rural environment Large family size High exposure to parasites Many infections Low antibiotic exposure Farming exposure High microbiological exposure
What is the biodiversity hypothesis?
Western lifestyle induces alteration of the symbiotic relationships with parasites and bacteria leading to dysbiosis of the microbiome at mucosal surfaces (gut)
Dysbiosis = compositional and functional alterations of microbiome Microbiome = the complete genetic content of all the microorganisms that typically inhabit in the body, such as the skin or GI tract
What is the allergic march?
Individual allergic disorders develop at different ages
- eczema and food allergy in infancy
- allergic rhinitis, conjunctivitis and asthma begin most often in preschool and primary school years
Do allergic disorders often overlap?
Yes
Many children with food allergy have eczema
Up to 80% of children with asthma have rhinitis
Is the presence of food allergy and eczema in infancy predictive of asthma and allergic rhinitis in layer life?
Yes
The progression = the allergic march
Does the prevalence of rhinoconjunctivitis increase or decrease with age?
Increase (a disease of adulthood)
Allergic rhinitis affects up to what percentage of adults?
30%
What approaches have been tried to interrupt the allergic march (with some evidence base)?
Avoiding the use of formula milk from cow’s milk to reduce the risk of eczema
Using probiotics during late pregnancy and lactation for preventing eczema
Early introduction of peanut or egg to the infant diet to prevent allergy to them (oral tolerance)
