Preventing Allergy

2. Preventing Allergy Allergy 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

3. Preventing Allergy Allergy Prevention – types • Primary Prevention :- by preventing sensitization to allergens (avoidance) • Secondary Prevention :- by preventing the onset of allergy in those who are already sensitized (atopics) • Tertiary Prevention :- by treating symptomatic patients to decrease complications or severity of disease.

4. Preventing Allergy Primary Prevention

5. Preventing Allergy Primary Prevention – Risk Factors • Age (early infancy exposure to allergen particularly during the first 3 – 6 month) • FH of allergy (if one parent allergic → 25 – 30% chance, if both are allergic → 50 – 80%) • Duration of exposure to allergen

6. Preventing Allergy Primary Prevention – Risk Factors 4. Degree of exposure to allergen 5. Active or passive exposure to tobacco smoke and other indoor pollutants

7. Preventing Allergy Primary 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)

8. Preventing Allergy Primary Prevention - Risk Factors in children Depend mainly on:- • timing of exposure • extent of exposure Prevention should focus on these factors which isn’t easy

9. Preventing Allergy Primary 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

10. Preventing Allergy Primary 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!!!

11. Preventing Allergy Primary 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

12. Preventing Allergy Primary Prevention – Breast-Feeding • To avoid food allergy use: • breast-feeding • OR alternative formulas like: a. extensively hydrolyzed b. amino acid formulas c. soya formulas

13. Preventing Allergy Primary 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

14. Preventing Allergy Primary 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)

15. Preventing Allergy Primary 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)

16. Preventing Allergy Primary 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)

17. Preventing Allergy Primary 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

18. Preventing Allergy Primary 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)

19. Preventing Allergy Primary 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)

20. Preventing Allergy Primary 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)

21. Preventing Allergy Primary Prevention – Weaning So……introduction of solid foods should be undertaken carefully

22. Preventing Allergy Primary 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

23. Preventing Allergy Primary 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

24. Preventing Allergy Primary prevention – Weaning Guidelines • Start with low allergen foods such as :-

25. Preventing Allergy Primary 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

26. Preventing Allergy Primary 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)

27. Preventing Allergy Primary 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

28. Preventing Allergy Primary 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

29. Preventing Allergy Primary Prevention – HDM avoidance in infants • The most effective way is to reduce exposure in beds • Plastic-coated mattresses may reduce count in beddings

30. Preventing Allergy Primary Prevention – HDM avoidance in infants • Infants should sleep on a new mattress • Infants bedding • to be washed each month in water >55 C • or use drying in hot clothes dryer

31. Preventing Allergy Primary Prevention – HDM avoidance in infants • Sheepskins and soft toys • avoidance in (bed, pram and car seat) • washed at 55 C or more

32. Preventing Allergy Primary 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

33. Preventing Allergy Primary Prevention – HDM avoidance in infants • Encase with high quality covers • Mattresses • pillows • also parents bed if infant sleep on it

34. Preventing Allergy 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)

35. Preventing Allergy 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)

36. Preventing Allergy 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)

37. Preventing Allergy 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

38. Preventing Allergy Secondary Prevention

39. Preventing Allergy Secondary 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??)

40. Preventing Allergy Secondary Prevention • Don’t appear to be practical for many reasons • The only exception is occupational allergy

41. Preventing Allergy Secondary 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

42. Preventing Allergy Secondary 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

43. Preventing Allergy Secondary 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

44. Preventing Allergy Secondary Prevention – association is an example • One study show it may be possible to delay progression from atopic dermatitis to asthma

45. Preventing Allergy Secondary 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

46. Preventing Allergy Secondary Prevention – examples • cat removal from young infants (12 month) with +ve SPT to cat • Result in –ve test to cat at 2 - 5 years

47. Preventing Allergy Secondary 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)

48. Preventing Allergy Secondary 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

49. Preventing Allergy Secondary Prevention – Occupational allergy Effective health surveillance is the best way

50. Preventing Allergy Secondary Prevention – OA - health surveillance • enables early identification of adverse health effects • environmental monitoring • risk assessment