In Australia, asthma is actually more of a problem of rural areas. And the world's highest rate of asthma is found in Tristan da Cunha, a remote South Atlantic archipelago, which is certainly not polluted, though maybe stressed which means that stress can bring on asthma. The disease is less prevalent among groups with poor hygiene than among those where washing is frequent. There is a theory that some infections give protection, but that remains unproven. At least as baffling is why the younger siblings in families are relatively protected from the disease compared to their older brothers and sisters, a pattern that seems to hold true everywhere.
Scientists are fairly certain what contributes to asthma susceptibility.
Exposure to allergens is a major factor, with the house dust mite a prime culprit. Secondhand tobacco smoke has also been blamed. Some studies show that lowered intake of fish may weaken asthma resistance. Some evidence suggests that intake of omega-3, a fatty acid found in fish oil, may be beneficial in keeping the disease away. Omega-3 has also been linked to healthy cardiovascular and immune systems and the development and functioning of the brain and eyes.