Industry expert Tony O'Lenick asks: What's the difference between irritation and sensitization? Steve Schwartz provides the answer…
Today when a consumer reacts to a topical product, their knee-jerk response is that they had an allergic reaction to the face cream, lipstick or whatever product they used. Given the state-of-the-art design in cosmetic formulation today, an allergic reaction is highly unlikely but an irritation response is possible. Therefore, it is important to understand the differences between irritation and sensitization.
Irritation is a chemical or mechanical surface reaction on skin that may occur immediately, such as in response to hot water or strong acid or base, or take some time to present like soap irritation. With the exception of strong mechanical or chemical reactions, an irritant response may or may not recur; it also can be affected by seasonal variation. For example, much more soap irritation is observed in winter because the skin has become somewhat compromised by the cold and dry weather. Irritant response also can be concentration-driven.
Sensitization is a warning mechanism designed to protect the body from a strong allergic reaction that can be fatal, such as a bee sting. It is an immune response that is slower to develop, taking 12 to 21 days of repeated exposures. A person can walk through poison ivy numerous times before experiencing the classic allergic response, as opposed to some irritant responses that can be immediate or take a short time to develop.
Once a person is allergic, he or she is always allergic. The body never forgets and exposure to a much lower concentration of allergen can cause an allergic reaction. Again, this is a good thing because the itchy rash initially brought on by contact with poison ivy is a minimal response and prevents people from further and continued exposure that could lead to a strong and possibly deadly reaction.
In summary and as an overview, an irritant is a surface response to a stimulant; an allergic reaction is a biochemical response to repeated exposures. Irritants can irritate one day and not the next, whereas an allergic response is forever.