Preventing Allergy Allergy Prevention Still we don’t have clear idea how to prevent allergy There...
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Transcript of Preventing Allergy Allergy Prevention Still we don’t have clear idea how to prevent allergy There...
Preventing Allergy
Allergy PreventionAllergy Prevention
• Still we don’t have clear idea how to prevent allergy
• There are certain measures and theories that can reduce the risk but still no certain means discovered
Preventing Allergy
Allergy Prevention – typesAllergy Prevention – types
• Primary Prevention :-Primary Prevention :- by preventing sensitization to allergens (avoidance)
• Secondary Prevention :-Secondary Prevention :- by preventing the onset of allergy in those who are already sensitized (atopics)
• Tertiary Prevention :-Tertiary Prevention :- by treating symptomatic patients to decrease complications or severity of disease.
Preventing Allergy
Primary Prevention – Risk FactorsPrimary Prevention – Risk Factors
1. Age (early infancy exposure to allergen particularly during the first 3 – 6 month)
2. FH of allergy (if one parent allergic → 25 – 30% chance, if both are allergic → 50 – 80%)
3. Duration of exposure to allergen
Preventing Allergy
Primary Prevention – Risk FactorsPrimary Prevention – Risk Factors
4. Degree of exposure to allergen
5. Active or passive exposure to tobacco smoke and other indoor pollutants
Preventing Allergy
Primary Prevention – Risk FactorsPrimary Prevention – Risk Factors
• Combining RF may greatly increase the risk
• concomitant exposure to passive smoking, cats or dogs and poorly ventilated home greatly increases the risk of sensitization to cats or dogs (Lindfors et al 1995)
Preventing Allergy
Primary Prevention - Risk Factors in childrenPrimary Prevention - Risk Factors in children
Depend mainly on:-
1. timing of exposure
2. extent of exposure
Prevention should focus on these factors which isn’t easy
Preventing Allergy
Primary Prevention-Risk Factors in childrenPrimary Prevention-Risk Factors in children
Hide et al study 1996:
• Newborns divided in 2 groups (exposed – not exposed) to HDM, pets and food allergens
• Followed for 12 month
Preventing Allergy
Primary prevention-Risk Factors in childrenPrimary prevention-Risk Factors in children
Hide et al study 1996:Results
• Allergy prevalence significantly lower in avoidance group compared to exposed group
• allergy was reduced but not eliminated, why we don’t know!!!
• May be avoidance was not complete, or other factors, unknown!!!
Preventing Allergy
Primary Prevention – Breast-FeedingPrimary Prevention – Breast-Feeding
• One of the common exposure to allergens in early life is food
• Infant formulas which contain cows milk are the commonest cause of food allergy
Preventing Allergy
Primary Prevention – Breast-FeedingPrimary Prevention – Breast-Feeding
• To avoid food allergy use:
o breast-feeding
o OR alternative formulas like:
a. extensively hydrolyzed
b. amino acid formulas
c. soya formulas
Preventing Allergy
Primary Prevention – Breast-FeedingPrimary Prevention – Breast-Feeding
Breast-feeding is the best alternative (cheap)
Promotion of breast-feeding as the most desirable means of infant feeding is an important health promotion strategy
Preventing Allergy
Primary prevention – Breast-Feeding in UKPrimary prevention – Breast-Feeding in UK
• Inspite the real importance of breast-feeding still < 50% of mothers start in infancy or continue it
• Even breast-feeding for only few days can offer some protection against cows milk allergy (Host et al 1988)
Preventing Allergy
Primary Prevention – Breast-Feeding AdvantagesPrimary Prevention – Breast-Feeding Advantages
• Breast-fed infants have lower serum IgE levels, less allergic illness in early childhood and possibly though to adolescence (Buonocore et al 1992, Burr et al 1993, Saarinen and Kajosaari 1995)
• Breast-fed infants are less sensitized to HDM at age one year (Kramer 1988)
Preventing Allergy
Primary Prevention – Breast-Feeding AdvantagesPrimary Prevention – Breast-Feeding Advantages
• Breast-fed infants have fewer respiratory symptoms than those not on breast-feeding (Woodward et al 1990)
• Significant risk ↓ of asthma at 6years if breast-fed was continued for at least 4 month after birth (Oddy et al 1999)
Preventing Allergy
Primary Prevention – Breast-FeedingPrimary Prevention – Breast-Feeding
Some studies found that preventive effects of breast- feeding can be enhanced by maternal avoidance of potential food allergens (eg: milk, egg, fish) while breast-feeding
Preventing Allergy
Primary Prevention – Breast-FeedingPrimary Prevention – Breast-Feeding
• However……not all studies show clear benefit in preventing allergic diseases
• No benefit of breast-feeding in preventing atopic dermatitis (Nakamura et al 2000)
Preventing Allergy
Primary Prevention – WeaningPrimary Prevention – Weaning
• Infant gut isn’t mature tell 3 month → food allergens reach blood unchanged
• So…….food allergens early in life increase risk of sensitization
• Early introduction of solid food precipitate atopic eczema (Fergusson et al 1981)
Preventing Allergy
Primary Prevention – WeaningPrimary Prevention – Weaning
• Parents educated to delay weaning up to 4 month of age
• This message should be focused more to high risk children (i.e. when one or both parents are allergic)
• Infants who are allergic to cows milk have increased risk of allergies to other foods (Hill et al 1994)
Preventing Allergy
Primary Prevention – WeaningPrimary Prevention – Weaning
So……introduction of solid foods should be
undertaken carefully
Preventing Allergy
Primary Prevention – Weaning GuidelinesPrimary Prevention – Weaning Guidelines
• Start one food at a time in pea-sized amounts
• Double the amount daily until an appropriate amount for the age is reached
• Introduce new foods only when the child is well
Preventing Allergy
Primary Prevention – Weaning GuidelinesPrimary Prevention – Weaning Guidelines
• Cease the food if there is a reaction
• Wait 3 days for symptoms before introducing another new food
• Continue the tolerated food regularly
Preventing Allergy
Primary prevention – Weaning GuidelinesPrimary prevention – Weaning Guidelines
1Apple6التفاحCarrotالجزر
2Pear7كميترىCourgette
3Rice8الرزChickenالدجاج
4Potato9البطاطاlamb and turkey اللحم
5Pumpkinالقرع
• Start with low allergen foods such as :-
Preventing Allergy
Primary Prevention – Weaning GuidelinesPrimary Prevention – Weaning Guidelines
• Don’t give citrus fruits until 9 month age
• Don’t give fish until 10 month
• Don’t give eggs until 12 month
Preventing Allergy
Primary Prevention – PeanutPrimary Prevention – Peanut
• Department of health guidelines advise pregnants and breastfeeders who have atopy to avoid peanuts up to 2 – 3 years
• Sensitization can occur before birth (Warner et al 1994)
• So…….its important to start preventive measures to peanut from early pregnancy
(Jones et al 1996)
Preventing Allergy
Primary Prevention – PregnancyPrimary Prevention – Pregnancy
Despite many studies still no firm evidence to support
dietary manipulation during pregnancy because:
• Allergen avoidance in pregnancy may lead to nutritional inadequacy
• Life restriction done only under care of experienced allergist, dietic supervision
Preventing Allergy
Primary Prevention – HDM avoidance in infantsPrimary Prevention – HDM avoidance in infants
• highest concentration found in beds
• babies spend long time in contact with beddings
• soft furnishings and carpets are important source
Preventing Allergy
Primary Prevention – HDM avoidance in infantsPrimary Prevention – HDM avoidance in infants
• The most effective way is to reduce exposure in beds
• Plastic-coated mattresses may reduce count in beddings
Preventing Allergy
Primary Prevention – HDM avoidance in infantsPrimary Prevention – HDM avoidance in infants
• Infants should sleep on a new mattress
• Infants bedding o to be washed each month in water >55 C
o or use drying in hot clothes dryer
Preventing Allergy
Primary Prevention – HDM avoidance in infantsPrimary Prevention – HDM avoidance in infants
• Sheepskins and soft toys
o avoidance in (bed, pram and car seat)
o washed at 55 C or more
Preventing Allergy
Primary prevention – HDM avoidance in infantsPrimary prevention – HDM avoidance in infants
• Sources of additional indoor humidity should be avoided
• Remove carpets from bedrooms and playrooms of infants, and he should not be placed on any carpet
• Vacuum cleaner (HEPA) filters should be used
Preventing Allergy
Primary Prevention – HDM avoidance in infantsPrimary Prevention – HDM avoidance in infants
• Encase with high quality covers
• Mattresses
• pillows
• also parents bed if infant sleep on it
Preventing Allergy
Primary Prevention – Tobacco Smoke (TS)Primary Prevention – Tobacco Smoke (TS)
• TS increase risk of children to develop allergy → so advice parents about stopping because it gives many health benefits
• Most smoking pregnants continue smoking after birth
• Maternal smoking increase risk of eczema and asthma (Kjellman 1981, Schafer et al 1997, Arshad et al 1993)
Preventing Allergy
Primary Prevention – Tobacco Smoke (TS)Primary Prevention – Tobacco Smoke (TS)
• Maternal smoking during pregnancy increase IgE in umbilical cord, predispose infants to subsequent sensitization (Magnusson 1986)
• SPT reactivity to allergens is significantly increased in children whose parents smoke (Weiss et al 1985)
Preventing Allergy
Primary Prevention – Tobacco Smoke (TS)Primary Prevention – Tobacco Smoke (TS)
• Evidence is weak that parental smoking increase risk of allergic sensitization in children
(strachan and cook 1998)
• Exposure to TS associated with sensitization to HDM (Plaschke et al 1996 and Nielsen et al 1994)
Preventing Allergy
Primary Prevention – Tobacco Smoke (TS)Primary Prevention – Tobacco Smoke (TS)
• TS increase risk of children who develop allergy
so advice parents about stopping TS because it gives many health benefits
Preventing Allergy
Secondary PreventionSecondary Prevention
• To prevent sensitized ones (atopics) to develop allergic disease
• To do this we need to screen children to determine who is sensitized and advice them about avoidance (do you think this is acceptable??)
Preventing Allergy
Secondary PreventionSecondary Prevention
• Don’t appear to be practical for many reasons
• The only exception is occupational allergy
Preventing Allergy
Secondary PreventionSecondary Prevention – why not practical ?
1. sIgE test:
• is not necessarily linked to the presence of allergy
• not reliable predictor of allergy severity or risk
• -ve results don’t mean that this person would not become sensitized at a later date
Preventing Allergy
Secondary PreventionSecondary Prevention – why not practical ?
2. We don’t know how many sensitized will develop allergy
3. We don’t know if avoidance measures can prevent sensitized persons develop allergy
Preventing Allergy
Secondary PreventionSecondary Prevention – association is an example
• Rhinitis preceded asthma in 45% of people with both, with 2 years gap
• Food allergy at age 2 years associated with higher risk of allergic rhinitis and asthma (Zeiger et al 1992)
• So…..identify allergic rhinitis or food allergy then use avoidance or immunotherapy to prevent asthma
Preventing Allergy
Secondary PreventionSecondary Prevention – association is an example
• One study show it may be possible to delay progression from atopic dermatitis to asthma
Preventing Allergy
Secondary PreventionSecondary Prevention – association is an example
ETAC study 1998 (ETAC=early treatment of atopic child)
• Cetrizine for 1- 2 years to atopic dermatitis children
• after 18 month → 50% drop of sensitization to grass pollen, HDM who develop asthma
• Is it Permanent benefit or simple Delay of asthma onset? → need further studies
Preventing Allergy
Secondary PreventionSecondary Prevention – examples
• cat removal from young infants (12 month) with +ve SPT to cat
Result in –ve test to cat at 2 - 5 years
Preventing Allergy
Secondary PreventionSecondary Prevention – Occupational allergy
You cant depend on atopy in secondary prevention for
several reasons:
• Atopy is very common (1/3 population) meaning you must prevent 1/3 population from work (not practical)
• Atopy isn’t adequate justification for refusing employment where there is exposure to sensitizers
(Newill et al 1986)
Preventing Allergy
Secondary PreventionSecondary Prevention – Occupational allergy
You cant depend on atopy in secondary prevention for
several reasons:
• Even if you exclude atopics from work, more people become sensitized than protected
• It is acceptable regime to refuse employment of asthmatics in work with respiratory sensitizers
Preventing Allergy
Secondary PreventionSecondary Prevention – Occupational allergy
Effective health surveillance is the best way
Preventing Allergy
Secondary PreventionSecondary Prevention – OA - health surveillance
• enables early identification of adverse health effects
• environmental monitoring
• risk assessment
Preventing Allergy
Secondary PreventionSecondary Prevention – OA - health surveillance
Give employees information about
1. hazardous substances to which they are exposed
2. symptoms that may result
3. potential long-term risks
4. Advice workers to report any symptom related to the occupational health service
Preventing Allergy
Secondary preventionSecondary prevention – OA - health surveillance
Measures that reduce workers exposure to occupational
sensitizers:
• improving ventilation systems
• use effective filters
• use protective equipments
(protect against respiratory or skin contact)
Preventing Allergy
Tertiary PreventionTertiary Prevention
treating symptomatic patients to decrease
complications or severity of disease
Preventing Allergy
Tertiary PreventionTertiary Prevention – Medications
appropriate medications to
• Control inflammation
• Relieve symptoms
Preventing Allergy
Tertiary PreventionTertiary Prevention - AII indications
• venom sensitive patients to prevent anaphylaxis to insect sting
• SAR: good long-term benefits
• Perennial asthma → results favor AII in perennial asthma, main concern is safety issue
Preventing Allergy
Tertiary PreventionTertiary Prevention - AII advantages
• reduce new sensitivities in children
• delay progression of rhinitis to asthma
Preventing Allergy
Tertiary PreventionTertiary Prevention – immunization
Influenza vaccine in asthmatics is recommended
Preventing Allergy
Tertiary PreventionTertiary Prevention – smoking avoidance
• Avoidance (active or passive) is beneficial for asthmatics
• tobacco smoke worsens lung function in asthmatics (Chilmonczyk et al 1993)
Preventing Allergy
Prevention Possibilities for the futurePrevention Possibilities for the future
o to identify those at risk for sever disease
o strategies for preventing development of symptoms
Preventing Allergy
Tertiary PreventionTertiary Prevention – pollution and asthma
• no conclusive evidence that atmospheric pollution is linked to atopy
• Atmospheric pollution increases bronchial hyperresponsiveness (Zwick et al 1991, Molfino et al 1991,
Andrae et al 1988)
• So…..anti-pollution measures may be of some benefit in improving asthma symptoms
Preventing Allergy
Air pollution as a cause for asthmaAir pollution as a cause for asthma
• Epidemiologically this isn’t conclusive till now (studies continue)
• Many studies before and after Germany unification 1990 (von Mutius 1992/4, Behrendt et al 1993, Nowak et al 1996, Weiland et al 1999)
• Studies in east Germany
Preventing Allergy
Air pollution as a cause for asthmaAir pollution as a cause for asthma
• Before 1990 - ↑↑↑ pollution, but ↓ asthma prevalence in children, with ↑ bronchitis and cough
• After 1990 – pollution ↓↓↓ with ↑ asthma, atopy prevalence
• These findings suggest that pollution causes bronchitis not asthma nor atopy