Lecture 12 - Infant and Child Allergies Flashcards
what is a allergy
when a person reacts to a substance in the environment that are harmless to most people
1 in how many people will develop allergies at some time during their life
1 in 5 people
1 in how many people will develop eczema during their life
1 in 10
what % of children have a food allergy
5-10%
what % of adults have a food allergy
2-4%
allergies can occur across the lifetime but
many develop when we are young
we are less likely to grow out of an allergy if
it develops later in life
what is atopic disease
a genetic tendency to develop allergic disease
a child / person with atopic disease produces
elevated IgE antibodies after exposure to environmental allergens
atopic diseases present with one or more of …
asthma, allergic rhinitis and eczema or hives
what is atopic dermatitis (ezcema)
inflammation of the skin - reddened, swollen, itchy, weeping skin
what is asthma
an allergic inflammation of the bronchial airways producing swelling, narrowing and mucus = leads to difficulty breathing
what is allergic rhinitis
also known as hay fever, is a type of inflammation in the nose which occurs when the immune system overreacts to allergens in the air
what is a food allergy
an immune mediated hypersensitivity reaction to a food
what is hive (urtucarua)
itchy, raised lumps on the skin, can occur anywhere on the body
what is generally the first atopic disease to occur
ezcema
up to what % of children with eczema have a progression to asthma and or rhino-conjunctivitis
up to 40%
what is atopic march
meaning if an individual develops eczema they will be more susceptible to developing asthma of food allergies
what % of infants with ezcema will develop a food allergy
40% will also develop food allergy
majority of children with asthma will develop symptoms by age
6 and many even develop symptoms by age 3
what is wheezing
a sign of asthma, high pitched, whistling noise that occurs naturally with exhaling
do all children who wheeze develop asthma
not all children who have wheezing develop asthma and not all children who have asthma wheeze
what is a immune mediated response
can either be IgE or non IgE mediated, but involves the immune system
what is IgE mediated response
involves antibodies, picked up with a skin prick test
what is a non IgE mediated response
immune response - centered usually in the gut less immediate, does not produce antibodies
what happens in IgE mediated food allergy
Immunoglobulin E antibody identifies food proteins and signals the immune system to react
what are mast cells
first line of defence
where are mast cells found
skin, lungs, nose, mouth, gut and blood
what do mast cells contain
contain histamines which are released and increase blood flow and cause inflammation
a food allergen is always a
protein
how many foods are responsible for 90% of allergic reactions to foods and what are they
9
- milk
- eggs
- fish
- shellfish
- tree nuts
- peanuts
- wheat
- soybeans
- sesame
what are the mild to moderate symptoms of a food allergy
- swelling of the face, lips or eyes
- hives or red welts on the skin
- red, watery eyes
- itchy mouth or throat
- vomiting
- diarrhoea
what are the severe symptoms of allergy (signs of anaphylaxis)
- difficulty breathing
- tongue swelling
- coughing, wheezing and shortness of breath
- baby becomes pale and floppy
what allergies are most likely to be outgrown
- cows milk (by around 5 years)
- egg (by around 5 years)
- wheat
- soy
which allergies are most likely present
- peanut
- treenut
- fish, shellfish
what % of infants with peanut allergy will have persistent allergy
approx 75%
what are non immune mediated reactions more commonly known as
food intolerances
do non immune mediated responses produce IgE antibodies after exposure
no
non immune mediated reactions include reactions to
non protein substances such as carbohydrates, chemicals, food additives, toxins and irritants
non immune mediated reactions are usually less
less immediate / delayed reaction up to 20 hours after a food is eaten
how is diagnosis of a non immune mediated reaction usually done
typically elimination and reintroduction
allergy testing is not used as
a screening tool because there can be false positives and this would result in exclusion of foods that would not be necessary to
what is a skin prick test
drop of the allergen is put over the top of a prick or scratch of the skin, positive is a weal is larger than 3mm
serum specific IgE blood tests measure the levels of
allergy antibody, or IgE produced when your blood is mixed with a series of allergens
what is a EAST test
Enzyme Allergosorbent Test (serum specific IgE blood test)
what is a RAST test
radio allergosorbent test (serum specific IgE blood test)
what is the scale of serum specific IgE blood test
0-6, where 6 is very high and 0 is not detected
what are the unorthodox testing methods (not supported in NZ)
- cytotoxic food testing
- vega testing
- kinesiology
- iridology
- pulse testing
- hair analysis
what is meant by unorthodox testing for allergies
these tests have no scientific basis, are unreliable and provide non reproducible results, there are high prevalence of false positives
adverse consequences of unorthadox testing methods
- false positives
- expensive
- result in unnecessary dietary avoidance, can lead to malnutrition in children
what are the possible explanations to the global rise in food allergies
- genetics and the environment
- hygiene hypothesis (less exposure to infection in early life)
- development of allergy to foods by skin exposure
- methods of food processing
- delayed introduction of allergenic foods
genetic influence of atopic disease is considered to be likely …..
multifactorial with offspring inheriting ‘atpoy genes’
if both parents are affected by an atopic disease what % of the offspring are likely to be affected
40% of the offspring are affected
how can environmental factors link to atopy disease
migration differences, low to high atopy country
what does hygiene hypothesis suggest
suggests that reduced exposure to infectious diseases and microbial products associated with a cleaner lifestyle has suppressed the natural development of the immune system
children become protected from allergens by eating the food …
early
children become allergic by
by skin exposure, in the absence of the protective oral exposure
what is dual allergen exposure hypothesis
skin and oral exposure to the food
the American Academy of Paediatrics (AAP) 2008 suggest what about the maternal diet in pregnancy and food allergies
no protective effect of maternal exclusion of common allergen foods during pregnancy on the development of atopic disease in infants
recent suggestions are what of the maternal diet and allergen foods during pregnancy
suggestion that the presence of maternal dietary proteins in amniotic fluid, cord blood and human milk might support the induction of tolerance towards solid foods in infants
what is the recommendation of the maternal diet and allergen foods during breastfeeding
exclusion of common allergen foods from the maternal diet is not recommended, as this has not been shown to prevent allergies
what is found with pregnancy and breastfeeding with a possible role in allergy prevention
up to 3 serves of oily fish per week may be beneficial, some evidence that omega 3 fatty acids during pregnancy and breastfeeding may help prevent eczema in early
there is moderate evidence about what during pregnancy and breastfeeding to help prevent eczema, this is controversial
moderate evidence that probiotics during pregnancy and breastfeeding may hlep prevent eczema in early life = controversial
if breastfeeding is not possible, what can be given and what is the evidence of soy or goats milk formula reducing allergies
a cows milk formula could be given if breastfeeding is not possible
there is no evidence that soy or goats milk formula reduces the risk of allergies compared to cows milk formula
what is the evidence for a protective role for partially or fully hydrolysed formulas for prevention of eczema, food allergy, asthma or allergic rhinitis
there is no evidence to support this
what beverages are not recommended for infants as the main source of milk before 12 months of age
regular cows milk, goats milk, soy milk, nut and cereal beverages are not recommended
common food allergens (including peanut) should be introduced in age appropriate form before when
before 12 months of age, including high risk infants
new common allergen foods should be introduced how
one at a time, around 1 or 2 days apart to detect problem foods
once a common allergen food is tolerated, what should happen
continue to regularly as part of a varied diet
what are the recommendations of skin treatment for infants
use skincare products that do not contain food protein
