Protection against allergic disease linked to early dog exposure; early fever,
from the Journal of Allergy and Clinical Immunology

MILWAUKEE - Exposure to dogs in the first year of life enhances the development of the immune system, which reduces allergic sensitization and atopic dermatitis, according to a study featured in the February 2004 Journal of Allergy and Clinical Immunology (JACI). The JACI is the peer-reviewed scientific journal of the American Academy of Allergy, Asthma and Immunology (AAAAI).

James E. Gern, MD, and colleagues from the University of Wisconsin-Madison, followed 285 infants from birth to one year, comparing pet exposure in the home with their cytokine secretion patterns and allergy indicators. The study found that home exposure to dogs, but not cats, in the first year of life was associated with a reduction in atopic dermatitis, an itchy skin rash common in allergic families, and also in allergen specific IgE (the allergic antibody) in the bloodstream at age one year. The prevalence of eczema, which is often the first manifestation of allergy, after one year was 12% in children exposed to dogs, compared to 43% in children with no exposure.

Researchers also discovered that dog exposure enhanced the production of interleukin-10 (IL-10), an immune system hormone with potent anti-inflammatory properties. In previous studies, IL-10 seems to inhibit the development of allergic diseases and asthma. Dog exposure accounted for a 48% increase in IL-10 when compared to infants with no dog exposure.

The findings raise the possibility that enhanced IL-10 responsible for the lower risk for allergic sensitization and atopic dermatitis. Greater understanding of mechanisms that modify immune development to promote tolerance in infancy might lead to new preventative strategies for allergic diseases.

Early fever protects against allergies
Children who have a fever before age one are less likely to develop allergies at age 6-7 years, according to a study featured in the February 2004 Journal of Allergy and Clinical Immunology (JACI).

L. Keoki Williams, MD, MPH, and colleagues from the Henry Ford Health System in Detroit, and the Medical College of Georgia, enrolled 835 children at birth to determine if fever before age 1 was associated with allergic sensitization later in life. Of the 835 children, 441 underwent clinical evaluation at age 6 to 7 years.

The study noted that fever was common in the first year of life, affecting 207 (46.9%) of the 441 children. By age one, there were 321 episodes of fever among these 441 children, most commonly associated with infection of the ears, upper respiratory tract, and lower respiratory tract.

When evaluated at age 6 to 7 years of age, 31.5% of the children had atopy (positive skin prick test), 39.2% had seroatopy (positive allergen-specific IgE test), and 45.8% had allergic sensitization (either atopy or seroatopy). Researchers discovered that allergic sensitization and atopic asthma were significantly less common among children who had fevers in their first year. They also found that each time a child had a fever; the odds of them developing allergies later in life were reduced.

These findings provide direct support for the hygiene hypothesis, which suggests that exposure to infections early in life decreases the risk of developing allergies. More information is needed about the types of infections that protect against allergies and the pathways by which they mediate their effect.

The AAAAI represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic disease. Established in 1943, the AAAAI has more than 6,500 members in the United States, Canada and 60 other countries. The AAAAI serves as an advocate to the public by providing educational information and a physician referral directory through its Web site at www.aaaai.org.

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EDITOR'S NOTE: These studies were published in the peer-reviewed, scientific journal of the American Academy of Allergy, Asthma and Immunology, but do not necessarily reflect the policies or the opinions of the Academy. To receive a copy of the study, please contact John Gardner (jgardner@aaaai.org) at 414-272-6071. For more information and access to the archive of past JACI news releases, visit the Media Center of the AAAAI Web site, www.aaaai.org.

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