Contact dermatitis classically has all of the following characteristics EXCEPT:

Contact dermatitis is an inflammatory skin condition that typically arises upon exposure to an irritant or an allergen, leading to characteristic signs and symptoms. The presence of edema is common in this condition as it reflects the localized inflammatory response. Additionally, a pruritic erythematous rash is a hallmark feature, which indicates both the irritation and the body's immune response to the offending agent.

One of the key aspects of contact dermatitis is that it can present asymmetrically, especially if the exposure to the irritant or allergen was localized to a specific area of the body; for example, a reaction may be seen only on the hands after contact with a particular chemical or plant. This means that the rash does not have to be symmetrical. Therefore, while edema, a pruritic erythematous rash, and a clear history of exposure to an irritant or allergen are typical characteristics of contact dermatitis, the symmetrical presentation is not a defining feature and can often vary depending on multiple factors, including the type of irritant and the areas of skin exposed.