Around 40% of people have genes that allow the development of allergies; this is thought to possibly be the remnant of an anti-parasitic defence mechanism.
An on-going study (no date or indication of country in my notes) on breast feeding mothers: from the instant of birth, mothers ate no eggs, milk, cheese, yoghurt, icecream, fish or nuts. When infants were weaned, these foods were introduced into their diet between 7 and 12 months. There was a large drop (c. 50%) in children who had a family history of allergies developing allergies themselves.
1997: New theory that the immune system has to learn to recognise viral infections in the early years and that immunisation and vaccination procedures and children being kept apart from others with infectious diseases are reducing its opportunity to learn, with the results that inappropriate (allergic) reactions are made.
Asthma: Children are usually around one year old before the first attack. Salt intake has a slight effect on asthma attacks - more salt in the diet, more and worse attacks; the most effect was seen on men and children. Oxides of nitrogen (from vehicles) in the air seems to facilitate attacks caused by other substances. [In Barcelona in the 1980s, a a series of asthma epidemics were caused by soy beans unloaded in port, an onshore breeze blew it into the city where an inversion layer trapped it. Only adults were affected and smokers 5 to 10 times more likely to be victims.]
Smoking: Smokers have 5% more chance of developing an allergy if smoking when first exposed to an allergen. The current increase (date not noted) in smoking in women of childbearing age could affect children in the first 12 months (the period now established as a window for sensitivity).
Various sources
