Which type of allergic effect occurs within hours and may involve symptoms like contact dermatitis?

The correct answer is associated with delayed-type hypersensitivity reactions that can manifest within hours to days after exposure. Type IV hypersensitivity involves T-cell-mediated immune responses rather than antibody involvement, which is characteristic of other types of allergic reactions.

In the case of contact dermatitis, this often occurs when the skin comes into contact with an allergen or irritant and the individual's immune system reacts. It is typically identified by inflammation, redness, and itching in the areas exposed to the irritant. This mechanism involves sensitization upon first exposure, followed by a more rapid immune response upon subsequent exposures.

The time frame for Type IV reactions often spans from 24 to 72 hours, which aligns well with the question's parameters of symptoms developing within hours. This is distinctly different from Type I, Type II, and Type III hypersensitivity reactions, which are mediated by antibodies and have different symptoms and timeframes associated with them.