For an individual to respond appropriately and protectively to harmful stimuli they need to be able to initiate adequate inflammatory and immune responses. The inflammatory response is part of the body's response to external stimuli and occurs when the innate protection of the skin or mucous membranes, otherwise known as the integument, is breached.

The body's innate defence mechanism is the individual's constant first line of defence and is present from birth. It is reliant on the body's natural barriers, skin and mucous membranes, preventing pathogens entering the body. In addition, these barriers actively recognize pathogens through the action of Langerhans cells embedded in the epithelium, which initiate a protective inflammatory response.

In contrast the acquired immune response develops at the time of primary exposure to specific infections, or when stimulated by exposure to antigens through immunization. Repeated exposures trigger the ‘memory’ of specialized cells provoking a targeted antibody-mediated response.