Final answer:
Contact dermatitis occurs as a result of an allergy to a substance that comes in direct contact with the skin, and is a type IV hypersensitivity reaction.
Step-by-step explanation:
When an allergy to a substance comes in contact with the skin, the condition that often occurs is contact dermatitis. This type of allergic reaction is considered a type IV hypersensitivity reaction, where the immune system responds to the substance after being sensitized to it. Common examples include allergic reactions to latex or the oils from poison ivy, which lead to an inflammatory response upon contact. In contrast, other conditions such as eczema or atopic dermatitis may be associated with allergic reactions but do not arise specifically because of contact with an allergen.
Conditions like psoriasis and seborrheic dermatitis are chronic skin diseases and are not primarily caused by contact allergens. Other options listed, such as erythema migrans or syphilis, are associated with infections, while a chancre is a sore typically associated with syphilis, not an allergic response.