Healthy Exposure to Allergens
There are four main routes that a person can be exposed to an allergen. (4, 5, 106)
- Orally
- Through the skin
- Through the gut
- Inhaled into the respiratory system
Immunological Barriers
Your body has barriers in place to screen everything that enters the body. The oral mucosa, skin layers, gut epithelium, and respiratory epithelium are the immunological barriers to these main routes of exposure.
Healthy barriers are noninflamed and functional; they allow entry to harmless things while impeding harmful things.
So how does the body know what is dangerous and what is not? Well, antagonists cause inflammation and bypass barriers. The immune system picks up on these signals and forms a response against things that display these patterns.
Your immune system isn't perfect; it can't pinpoint the culprit in all cases. If it detects a harmless allergen in the proximity of inflammation, it can mistakenly form a response against it. Also, if a nonfunctional barrier allows a harmless allergen to enter, the immune system can assume it maliciously bypassed the barrier and generate a response.
Thus, it is crucial to keep these barriers in good condition as abnormal development or damage to these immunological barriers increases the risk of allergic development.
Tolerance Induction
Luckily, to prevent the development of an allergy to everything you touch, eat, or breathe, the immune system naturally develops tolerance towards things that it consistently finds non-intrusive and in the absence of inflammation. Essentially, through healthy barriers, your body can accurately learn what is harmless and ignore it.6
Infancy is the most influential phase in training the immune system. Development of tolerance to allergens is driven by regular, early exposure during a 'critical early window' of development. This window appears to be between 4 and 6 months of life, and delaying exposure beyond this period increases the risk of developing allergies.7