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Page 1: Preventing Allergy
Page 2: Preventing Allergy

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

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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.

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Preventing Allergy

Primary PreventionPrimary Prevention

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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

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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

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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)

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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

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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

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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!!!

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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

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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

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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

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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)

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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)

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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)

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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

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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)

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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)

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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)

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Preventing Allergy

Primary Prevention – WeaningPrimary Prevention – Weaning

So……introduction of solid foods should be

undertaken carefully

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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

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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

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Preventing Allergy

Primary prevention – Weaning GuidelinesPrimary prevention – Weaning Guidelines

1Apple6التفاحCarrotالجزر

2Pear7كميترىCourgette

3Rice8الرزChickenالدجاج

4Potato9البطاطاlamb and turkey اللحم

5Pumpkinالقرع

• Start with low allergen foods such as :-

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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

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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)

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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

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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

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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

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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

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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

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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

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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

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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)

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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)

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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)

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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

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Preventing Allergy

Secondary PreventionSecondary Prevention

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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??)

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Preventing Allergy

Secondary PreventionSecondary Prevention

• Don’t appear to be practical for many reasons

• The only exception is occupational allergy

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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

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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

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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

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Preventing Allergy

Secondary PreventionSecondary Prevention – association is an example

• One study show it may be possible to delay progression from atopic dermatitis to asthma

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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

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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

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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)

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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

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Preventing Allergy

Secondary PreventionSecondary Prevention – Occupational allergy

Effective health surveillance is the best way

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Preventing Allergy

Secondary PreventionSecondary Prevention – OA - health surveillance

• enables early identification of adverse health effects

• environmental monitoring

• risk assessment

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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

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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)

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Preventing Allergy

Tertiary PreventionTertiary Prevention

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Preventing Allergy

Tertiary PreventionTertiary Prevention

treating symptomatic patients to decrease

complications or severity of disease

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Preventing Allergy

Tertiary PreventionTertiary Prevention – Medications

appropriate medications to

• Control inflammation

• Relieve symptoms

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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

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Preventing Allergy

Tertiary PreventionTertiary Prevention - AII advantages

• reduce new sensitivities in children

• delay progression of rhinitis to asthma

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Preventing Allergy

Tertiary PreventionTertiary Prevention – immunization

Influenza vaccine in asthmatics is recommended

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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)

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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

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Preventing Allergy

Controversial AreaControversial Area

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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

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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

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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

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