A Person Is Having Skin Testing Done to Assess for Allergies

A person is having skin testing done to assess for allergies. What would be evidence of exposure to an antigen?

A) A response that only appears 5 days later
B) Itching at the site of the skin test
C) An area of approximately 1 mm of induration and erythema
D) An area of greater than 10 mm of induration and erythema