The so-called hygiene hypothesis suggests that that lack of exposure to dirt and germs in early childhood increases a person's susceptibility to allergies and illnesses.
Findings of a new study appear to reinforce this idea as researchers find that farm dust can protect children against asthmas and allergies. The discovery could eventually pave way for the development of an asthma vaccine.
Years ago, it was found that kids who grew up on farms have far better protection from asthma and allergies albeit scientists were not able to pinpoint what is responsible for this.
Now, researchers said that they have identified the link between farm dust and protection against asthma and allergies.
For their study, Bart Lambrecht, from Ghent University Hospital in Belgium, and colleagues used dust from dairy farms in Europe that were laden with bacteria and fungi. They injected small amounts of farm dust bacteria dubbed endotoxins into the noses of mice and discovered that this triggered immune reaction in the form of inflammation.
The researchers found that the mice that had the reaction did not develop asthma later on regardless that they were exposed to house dust mites, which are known to notoriously set off asthma.
The researchers likewise discovered that farm dust causes the mucous membrane found inside the respiratory tract to have less severe reactions to allergens because of a protein known as A20, which is produced by the body when a person gets in contact with farm dust.
The researchers said that the protective effect disappeared after the protein was inactivated in the animals as it left the mucous membrane of the lungs incapable of reducing asthmatic or allergic reactions.
"The farming environment protects from allergy by modifying the communication between barrier epithelial cells and DCs through A20 induction," the researchers reported in their study published in the journal Science on Sept. 4.
Lambrecht and colleagues examined 2,000 individuals who grew up on farms and found that most did not suffer from asthma or allergies. They also found that those who remain prone to allergies and asthma were deficient of the protein.
Lambrecht said that those who still develop allergens have a genetic variant of the A20 gene which results in A20 protein to malfunction.
What the researchers intend to do next is look for the active substance present in farm dust that provides protection since this can be used to develop a vaccine against asthma.
"Discovering how farm dust provides this type of protection has certainly put us on the right track towards developing an asthma vaccine and new allergy therapies," said study researcher Hamida Hammad, from Ghent University.
