Allergies Flashcards
How common are allergies
20% of the population have allergies
What is Atopy
an inherited tendency for an exaggerated IgE antibody response to common environmental antigens.
- positive skin rick to one or more allergens
- family hx of allergic disorders
If a patient is allergic to peanuts what are other allergies should you consider in them.
50% of patients will have an allergy to tree nuts as well - walnuts, and almonds.
If a patient is allergic to latex what other allergens may they have
they may have sensitivity to certain fruits - banana, avocado or kiwifruit
What are the common ways that an atopic patient will manifest an allergic disorder
allergic rhinitis, asthma, atopic dermatitis, allergic gastroenteropathy
What are the common sources of allergens (inhaled, food, other)
Inhaled - pollens, domestic animals, house dust mites mould spores, cockroaches
food - peanuts, fish, shellfish, milk, eggs, wheat, (NOT THE SAME AS FOOD INTOLERANCE.
other - drugs, allergens insect venoms, occupational
How/when do atopic disorders present
immediate food hypersensitivity @ 0-1yrs
Atopic Dermatitis - (1-3yrs)
asthma @ 7-15yrs
allergic rhinitis 7-15yrs
What are the four main types of allergic reactions
- Type 1 - anaphylaxis / Immediate - IgE & mast cell mediated response to allergen eg. asthma
- Type 2 - antibody to fixed antigen - Antibody (IgG/M) and complement eg autoimmune dx
- Type 3 - immune complex disorders - Immune complexes e.g., vasculitits
- Type 4 - cell mediated - T-Cell mediated (delayed type) e.g. contact dermatitis
How does Type 1 Allergic Reaction Occur
Type 1 is a IgE & mast cell reaction. IgE is attached to the surface of mast cells and when they combine with a specific allergen causes a release by degranulations of chemical mediators (histamine, SRS-A etc) which then cause the symptoms.
How does Type 2 Allergic Reaction occur
+++++++
How does a food allergy present
Often in infancy and childhood
Main symptoms may be severe urticarial type reactions through to gastrointestinal symptoms such as - anorexia, nausea, vomiting, spitting up food, colic, diarrhoea, failure to thrive
what are the two types of food allergy?
immediate (within 2hrs), delayed (up to 24-48hrs post)
What is the difference between and intolerance and a food allergy
???????
what are some clinical features of an IgE mediated food reaction
urticaria - facial or generalised dizziness and confusion wheexe itchy, runny, nose and eyes itchy throat flushing or blotchiness/pallor (if severe) angiodema of face and airway vomiting, diarrhoea and abdo colic usually in infants and toddlers
When does food allergies normally resolve by?
5-7yrs
what are the 3 big causes of food allergies?
Cow’s milk, eggs, peanuts
when is it ok to introduce eggs to children?
avoid until 2years (including in cakes etc) then introduce cautiously - e.g. in cakes
all vaccines are safe (MMR has a minuscule amount)
how do you test for allergies
Skin prick testing is first line - neg test is useful for excluding an IgE mediated allergy
RAST blood test to detect serum specific IgE ( expensive therefore done when - skin prick and Hx not adding up, extensive Eczema, dermographism, infants and very young children, immunotherapy work up)
What drug options are there for allergy control?
Antihistamines (H1/H2 receptor antagonists)
Adrenaline - emergency
sympathometics, some anticholinergics, steroids, sodium cromoglycate.
when does hay fever usually develop (age)
50% have it by 15yrs and 90% by 30yrs
How does Hayfever present
widespread itching (nose, throat and eyes) is common however those with perennial rhinitis rarely have the eye and throat involvement (more just sneezing and watery rhinorrhea, they are more likely to develop nasal polyps.
What are treatment options fro hay fever (seasonal allergic rhino conjunctivitis)
- Antihistamine (oral - not much use in vasomotor rhinitis, intranasal - rapid action, opthalmic)
- decongestants (topical or oral - get rebound congestion from topical)
- sodium cromoglycate (intranasal - pwder, spray, opthalmic drops for conjunctivitis)
- Corticosteroids (intranasal - not so effective for non-eosiniphilic vasomotor rhinitis, oral - very effective if other methods fail, opthalmic drops for allergic conjunctivitis)
