Summary and Review of the article “Update on allergies in pregnancy, lactation, and early childhood” by I. Pali-Scholl, H. Renz, and E. Jensen-Jarolim (Journal of Allergy Clinical Immunology 2009;123:1012-21).

 

One of the most commonly asked questions by young families is how to possibly prevent the development of allergy in the next child. In fact you can see such a question asked on my last post. This is an agonizing question for a pediatric allergist. The specialty of pediatrics and of allergy is very focused on prevention. We immunize to prevent illness, we educate to prevent injury, and we identify allergens relevant to allergic illnesses to direct avoidance measures. When we have identified an allergic child we advocate secondary or tertiary prevention. Specifically we advocate staying away from things that you are sensitized to and things that have caused problems. What is needed is primary prevention of allergy.

 

Primary prevention would be stopping allergy before it develops in a young child. There are a number of thoughts and ideas on what works best, however for the most part there is no failsafe way to prevent the development of allergy. Most of the time recommendations involve rather drastic elimination/avoidance measures which all too often may have an adverse effect on the quality of life for the child and the family. The medical evidence to support these recommendations is continuously changing. In some instances it never existed. A recent article in the Journal of Allergy Clinical Immunology provides an update on these primary efforts to prevent allergy in young children and in the mothers during pregnancy. This paper focused on the effect of the mother’s immune status on the development of allergy in the child.

 

The article looked at risk factors for the increase in allergy in the mother during pregnancy, risk factors for sensitizing the child to an allergen, and preventative measures to avoid allergy induction. There is a succinct summation and a few notes on what the future looks like at the end of the article. My reviewer’s prerogative allows me to be selective. I will forgo a discussion on the development of allergy in the mothers and focus on the children.

 

Risk Factors for Sensitization in the Child:

Remember a risk factor is an association only. It does not determine cause. The establishment of a relative risk directs a search for the cause.

There were 11 topics reviewed;

  1. Diet of the mother during pregnancy
  2. Exposure to tobacco smoke
  3. Exposure to alcohol
  4. Treatment with antibiotics
  5. Insufficient exposure to environmental bacteria
  6. Diet of the mother during lactation
  7. Prematurity and low birth weight
  8. Exposure route to antigens
  9. Breast-feeding, formula diet, and introduction of solid food
  10. Mode of birth
  11. Epigenetic influences (gene-environment interactions)

 

1. Diet of the mother during pregnancy– The article has a table of references dealing with a wide variety of food associations-maternal ingestion and outcomes in children. The number in parentheses is the number of references that claimed the association. The use of these foodstuffs was associated with…..

n-6 Polyunsaturated Fatty Acids (PUFA) – increased risk of eczema (2)

Celery and citrus fruits- increased risk of food sensitization (1)

Vegetable oil, raw sweet pepper, citrus fruit- more inhalant sensitization (1)

Nuts – more wheezing, steroid use, asthma (1)

Overall high energy and lipid intake- more sensitization, asthma (2)

Probiotics- No effect on atopic dermatitis at 2 yrs, increased wheezing (1)

As you can see, there is not a substantial literature on this topic. The authors point out that for children without a first-degree relative (parent or sibling) with allergy there is no benefit from special nutritional interventions during pregnancy, during lactation, or during the first year of life

 

2. Exposure to tobacco smoke– Four articles support the finding that smoke exposure of the mother during pregnancy leads to higher IgE levels (the antibody associated with allergy), eosinophils (an inflammatory cell associated with allergy), airway disease and wheezing episodes in the child.  Of note is the observation that the risk of causing specific IgE to inhalant or food allergens was especially increased in children born to non-allergic parents who were exposed to cigarette smoke in the first two months of life. Usually allergy follows a family history of allergy, however cigarette smoke exposure appears to trigger sensitization in those children not genetically predisposed.

 

3. Exposure to alcohol– elevated IgE levels in the children.

 

4. Treatment with antibiotics – two studies have shown that there is more wheezing, more allergy skin test reactivity, and more specific IgE in children who were exposed to antibiotics early in life. The theory here is that there is a disturbance of the good bacteria in the gut by the antibiotics which leads to altered develop of the gut’s immune system.

 

5. Insufficient exposure to environmental bacteria– this concept is part of the hygiene hypothesis for the development of allergy and yes it is insufficient or not enough exposure to bacteria. When there is not enough environmental bacterial exposure early in life, the immune system develops towards allergic responses. In this model, more frequent acute respiratory tract infections in the first 9 months of age reduces asthma, eczema, hay fever, allergic sensitization, and total IgE levels. More environmental bacteria exposure is good (at least for not going on to develop allergy).

 

6. Diet of the mother during lactation– contrary to the usual dogma, food exposure may be necessary to develop tolerance (vs. sensitization) to a food. The reference for this statement is an evidence-based review of the literature published in 2006. This review did not find any strong evidence for allergen avoidance during lactation (or pregnancy) in preventing the development of allergy in young children. Clearly more work is necessary in this area.

 

7. Prematurity and low birth weight– there is no association with an increased risk of developing food allergy. The risk for inhalant allergens has not been studied.

 

8. Exposure route to antigens– skin exposure is an excellent way to cause sensitization. Environmental skin contact to a food can lead to allergic sensitization whereas oral intake could induce tolerance. This is a fascinating concept. If the food sensitizations are occurring due to skin contact, then where/when/how is this happening?

 

9. Breast-feeding, formula diet, and introduction of solid food– less breast feeding and the early introduction of solid foods had been a confounder in the development of allergy. Only in high-risk babies did breast feeding for 4-6 months, the use of extensively hydrolyzed formula, and the avoidance of solid foods and cow’s milk worked to prevent atopic dermatitis and cow’s milk allergy until age 2 years. This did not work beyond 4-6 months of age. The negative effect of early introduction of solid food has not been confirmed by an evidence-based review of the literature.

 

10. Mode of birth– two studies suggest that birth by caesarian section increases the risk for nasal allergy, wheezing episodes, and having food-specific IgE.

 

11. Epigenetic influences (gene-environment interactions)- a number of risk factors have been discovered. These include diesel exhaust, wood smoke particles, road traffic, and tobacco smoke. More work has been done looking at xenobiotic chemicals, endocrine disruptors, heavy metals, and low-dose irradiation.

 

Suggestions to decrease the risk of developing allergic sensitization-

Avoidance of tobacco smoke by the mother and the child

Avoidance of alcohol during pregnancy and lactation

Eat a well-balanced diet; no special diet is needed unless there is a known food allergy

Avoidance of animals and dust only if allergy already exists

Avoidance of solid food until 4 months of age

Avoidance of nonprescription drugs, self-medication, and dietary supplements

           

Summary

The list of what should be avoided for a growing child has shortened due to the appearance of more controversial studies and a re-asking of the critical questions. What has stood the test of time is the continued recommendation to avoid tobacco smoke and alcohol. No special diet is needed by the mother during pregnancy or lactation unless the mother or the child already has a known sensitization/food allergy. The avoidance of pets, house dust, contact allergens, or medications is only recommended for those known to be already sensitive to these things. Exclusive breast feeding is recommended for at least 4 months but no longer than 9 months. The special hypo-allergenic formulas, those that have extensively hydrolyzed protein or are amino acid-based should be used for high-risk children to prevent atopic dermatitis or in one who already has this condition.

 

This is a tough area. We all want to do anything we can to prevent the development of allergy. The recommendations have changed over time. The allergist needs to keep track of these advances in our understanding of allergy prevention. The new recommendations follow the trend of using evidence-based medicine. These reviews have shown us no substantial evidence to support previous recommendations regarding the prevention of allergy in children. This is a very rich area of interest for many families and for research. I am confident that we will be seeing better studies. When these finally arrive be ready for more changes in what we recommend.

Fred Leickly

June 28, 2009 · fleickly · No Comments
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