Toxic effects can be classified into several categories, including acute, chronic, carcinogenic, teratogenic, and allergic. Acute toxicity refers to immediate adverse effects following a single exposure, while chronic toxicity results from prolonged exposure to a toxicant. Carcinogenic effects involve the potential of a substance to cause cancer, and teratogenic effects relate to the potential to cause developmental abnormalities in a fetus. Allergic effects are immune responses that occur upon exposure to certain substances.