Hygiene hypothesis and allergic diseases - a Twitter summary from the 2011 ACAAI meeting

This summary was compiled from the tweets posted by some of the allergists who attended the 2011 ACAAI meeting. The tweets were labeled #ACAAI. The text was edited and modified by me.

Farm animal exposure

Farm animal exposure in utero reduces risk of atopic dermatitis (AD). Risk reduction may occur through a TLR mechanism. Multiple different animals are more protective. Diversity of bacteria in farm homes may be the protective factor against atopy.

Children living on a farm are at reduced risk of asthma (OR 0.68), hay fever (OR, 0.43), atopic dermatitis (OR, 0.80), and atopic sensitization (OR, 0.54) http://goo.gl/qVY2G

Pets may be protective

Teens who had cats in the 1st year of life had a decreased risk of cat allergy at the age of 18. Dog exposure may be more protective against all forms of allergy not just allergy to dogs. It could be similar to the barnyard protection against atopic disease. Related reading: Getting a cat increases allergy risk in adults - getting one in adulthood nearly doubles the risk. Reuters and JACI, 2012.

Frequent washing

Dr. Platts Mills reviewed data that frequent washing, especially with soap, may be harming the skin barrier which may lead to increased sensitization. He suggested that daily bathing of infants may contribute to rising prevalence of atopy - hygiene hypothesis may be true.

Avoid soap in atopic dermatitis. It is best to use non-soap cleansers. They usually do not contain sodium lauryl sulfate (SLS), a chemical that creates soap’s foaming action and can dry and irritate skin. Non-soap cleansers include Dove Sensitive Skin Unscented Beauty Bar, Aquaphor Gentle Wash, Aveeno Advanced Care Wash, Basis Sensitive Skin Bar, CeraVe Hydrating Cleanser, and Cetaphil Gentle Cleansing Bar.

Epidemiological data

Hay fever data did not show much difference between 1955 and 1995 from Hal Nelson's data but asthma had a much bigger increase. What are the causes for asthma increase during that period? Some experts suggest it could be lack of exercise, obesity, changing indoor environment, or even lack of deep breathing while watching TV. Obesity increases the risk of AD two-fold. Prolonged obesity is worse. Pro-inflammatory issues likely play a role (similar to asthma).


- Bostock in 1819: Allergy is a rare disorder of the privileged class in the UK.
- NHANES data shows 2-5-fold increase in atopy from the 1980's to the 1990's.

With 30% of the population being atopic can we still consider it a disease, asks Phil Lieberman.

There is an inverse correlation between parasite exposure and atopic responses, most recently suggested by data from the former East Germany.

Even in Africa where the asthma rates are low there is an urban affluence link to high positive dust mite sIgE titres. In Costa Rica there is a similar pattern where the water is cleaner, shoes are common and helminths are eradicated but there is more asthma.

In Venezuela children treated for worms were noted to have increased atopic rates that improve with re-infection.

There is a possible link between the lack of omega 3 fatty acids and the risk for atopy. However, supplementation studies in active atopic disease were disappointing.

This summary was compiled from some of the tweets posted by Dr. David Fischer @IgECPD4, Robert Silge, MD, @DrSilge, Danny Ramirez, MD @allergysa, and a few others. The tweets were labeled #ACAAI and they reached more than 10,000 people. I would strongly encourage you to post updates on Twitter from the CME conferences that you are planning to attend in the future. Disclaimer: The text was edited, modified, and added to by me.

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