This may lead to leaky gut and excessive stimulation of the immune system. (perfecthealthdiet.com)
For those reasons, processed foods may cause inflammation and over stimulation of the immune system which, after longer exposure, may contribute to a chronic disease. (ntoi.ie)
Some vaccines are given locally, for example into the nose, but most require injection so that the maximum stimulation of the immune system is achieved. (springcreekanimalhospital.com)