Allergic diseases are on the rise worldwide. Reasons for this epidemic are not clear.
Several intervention studies to examine the effects of indoor allergen elimination on the incidence of asthma are underway in children followed prospectively from birth. The results will impact public health policies because they will discover whether considering indoor allergen elimination as an important element of primary prevention of various allergic diseases is meaningful.
Allergic march is an important idea to understand. According to this concept, allergic diseases occur from a two-step process: a first phase of sensitization followed by development of allergic diseases. The sensitization refers to formation of IgE, or Immunoglobulin E, antibody proteins to various substances one faces during the first few years of life. This is arbitrated by the body's immune system under the influence of genes that are inherited from your parents.
Sensitization to allergens often occurs in the following order: first to food allergens (milk and eggs), next to indoor allergens (animal dander and dust mites) and finally to outdoor allergens (pollen). It is important to understand that sensitization does not always result in allergic diseases.
Some children (but not all) who are thus sensitized go on to develop allergic diseases. Atopic dermatitis (a.k.a eczema) is often the first expression of allergic disease in children. Eighty percent of children who develop atopic dermatitis do so during the first year of life. Forty percent outgrow eczema by 3 or 4 years old. Another 40 percent will have intermittent disease, and only 20 percent will develop persistent disease into adulthood.
It is important to realize that 75 percent of children who have eczema as toddlers will develop allergic rhinitis (hay fever), and 50 percent will develop asthma during school-age years.
Prevention and deacceleration
The following tactics may prevent or slow down sensitization and development of allergic diseases. Breast milk has many advantages over formula feeds. One of them is allergy prevention.
The European Academy of Allergology and Clinical Immunology recommends only breast-feeding for 4 to 6 months irrespective of family history of allergy. The American Academy of Pediatrics recommends that pregnant and lactating women should avoid eating foods containing peanuts to prevent peanut allergy in children.
Some foods have more allergy-causing potential than others do. Keeping this in mind, many experts recommend that solid foods are best introduced in your infant's diet not before 6 months of age and in the following order: Introduce baby cereals, vegetables and fruits between the ages of 6-12 months; cow's milk and meat (beef, chicken, turkey or pork) after 12 months; foods containing eggs after 18 months; and foods containing peanuts, tree nuts, fish and seafood after 36-48 months of age.
For several years, the use of hydrolyzed infant formula (where milk proteins are predigested into small peptides or amino acids) was recommended as an alternative for infants, for whom breast milk was not available and who were genetically predisposed to atopic diseases. A German Infant Nutritional Intervention study showed that use of hydrolyzed formulas compared with unhydrolyzed infant formulas resulted in a lower incidence of atopic eczema during the first three years of life.
Indoor allergy prevention
A prospective study from Germany suggests there is an increased risk of allergen sensitization in children whose mothers smoked up to the end of their pregnancies and continued to smoke after childbirth, especially in families with strong history of allergy. If you are smoking and become pregnant or are planning to become pregnant, this may be a perfect opportunity to quit smoking to help your baby grow normally and have fewer allergies.
Avoiding exposure to dust mites and animal dander has shown variable results in preventing allergies. Some studies show benefit, others do not. It might be possible that exposure to cats, dogs and dust mites early in life has a harmful effect only on children who are genetically predisposed to developing allergy to these allergens and not in others. Since the current technology does not help us to recognize such children at risk early, it is safer to avoid exposure to cats, dogs, other animals and dust mites if your family has strong history of allergy and asthma.
Allergy screening for common allergens by doing allergy skin tests (like screening for lead) is recommended for children coming from families with strong allergy and asthma history between the ages of 2 and above. This will help us identify children at risk for whom vigorous implementation of allergy control measures may be beneficial.
Natarajan Asokan, M.D., F.A.A.P. is a board-certified allergist and immunologist and a board-certified pediatrician with more than 25 years of experience as a physician and 10 years of experience as a practicing allergist and immunologist. He can be reached at 1739 Beverly Ave., Suite 118, Kingman, AZ 86409, or (928) 681-5800.