A study in the New England Journal of Medicine shows that children who grow up in extremely clean homes are far more likely to develop asthma and allergies than those who grow up in farms and dirty homes. Another study in Lancet from rural Austria showed that children who are exposed to horses and stables before they are one year old have a much lower incidence of asthma, hay fever and an allergic skin disease called atopic dermatitis. A third study in the Journal of the American Medical Association shows that exposure to two or more cats or dogs in the first year of life lowers risk of having allergies to dogs and cats. Several studies from Greece, Germany and France show that children who are brought up on farms are less likely to be allergic than those brought up in cities. Three months ago, a study from Michigan State University showed that children who have lots of older brothers and sisters are the ones least likely to develop childhood asthma and other allergic diseases.

All of these studies show that exposure in the first year of life to dirt, filth, bacteria, viruses, cats, dogs, farm animals and animal manure helps to protect children from developing asthma and allergies to animals and pollens. Nobody knows what causes asthma. A prevailing theory is that you have an immune system that is supposed to kill germs. If your immune system doesn’t have a lot of germs to kill when you are very young, it may start attacking things that are not germs, such as pollen, dust, animal dander and foods. These studies show that children whose immunities have nothing to do, go out and make something to do.

But that really doesn’t explain why exposure to something in the first years of life helps to prevent asthma and allergies, but exposure to these same things many years later causes allergies. The study in the New England Journal of Medicine shows that children with the highest level of endotoxin in their mattresses were the ones least likely to develop asthma and allergies. Many bacteria contain endotoxin in their bodies. When bacteria cause an infection in you, they release the endotoxin into your blood stream, which can cause a very high fever and make you very sick. For example, children can die from endotoxins from pneumococcus that gets into the bloodstreams and sends them into shock.

A promising unproven theory today is that exposure to small amounts of endotoxin in the first year of life causes your immunity to practice on this endotoxin and it learns how to attack only foreign bacteria and their components. But if your immunity cannot practice on large mounts of endotoxin in the first few years of life, it gets restless and starts to practice on anything that gets into your nose. It attacks ragweed pollen so you get itchy eyes and nose every August and September. It attacks the skin from a cat so you sneeze and itch when you breathe in the dander from a cat. It attacks fragments of a small mite in dust that get into your nose to make you wheeze, and so forth. But this is just a theory. Nobody recommends now that you take your one-year old and expose him to the manure of animals to expose him to lots of endotoxin; that could make him very sick. Let’s see what future studies show.

1) NEJM Septebmer 19, 2002.

2) Does living on a farm during childhood protect against asthma, allergic rhinitis, and atopy in adulthood? American Journal of Respiratory and Critical Care Medicine, 2001, Vol 164, Iss 10, pp 1829-1834. B Leynaert, C Neukirch, D Jarvis, S Chinn, P Burney, F Neukirch.

3) Crete: does farming explain urban and rural differences in atopy? Clinical and Experimental Allergy, 2001, Vol 31, Iss 12, pp. 1822-1828. M Barnes, P Cullinan, P Athanasaki, S Macneill, AM Hole, J Harris, S Kalogeraki, M Chatzinikolaou, N Drakonakis, V BibakiLiakou, AJN Taylor, I Bibakis.

4) Farming, rural lifestyle and atopy in adults from southern Germany – results from the MONICA/KORA study Augsburg. Clinical and Experimental Allergy, 2001, Vol 31, Iss 12, pp 1829-1838. B Filipiak, J Heinrich, T Schafer, J Ring, HE Wichmann. Filipiak B.

5) Exposure to farming in early life and development of asthma and allergy: a cross-sectional survey. Lancet, 2001, Vol 358, Iss 9288, pp 1129-1133. J Riedler, C BraunFahrlander, W Eder, M Schreuer, M Waser, S Maisch, D Carr, R Schierl, D Nowak, E vonMutius. Riedler J, Childrens Hosp, Muellner Hauptstr 48, A-5020 Salzburg, AUSTRIA.

6) Does a higher number of siblings protect against the development of allergy and asthma? A review. Journal of Epidemiology and Community Health, 2002, Vol 56, Iss 3, pp 209-217. W Karmaus, C Botezan. Karmaus W, Michigan State Univ, Dept Epidemiol, 4660 S Hagadorn Rd, Suite 600, E Lansing,MI 48823 USA

Checked 8/9/05