Which organism's bite can lead to an allergic skin reaction?

All of the listed organisms—ants, fleas, and spiders—can indeed lead to allergic skin reactions in certain individuals. Each of these creatures has different methods of delivering substances that can cause allergic responses.

Ants, particularly fire ants, inject venom that can cause intense itching, swelling, and in some cases, anaphylaxis in highly sensitive individuals. Fleas can also provoke allergic reactions, primarily due to their saliva, which contains proteins that can cause localized inflammation and discomfort in sensitive people. Spiders, while often considered less of a threat, can also cause allergic reactions, though the severity varies depending on the species and the individual’s sensitivity to spider venom.

Given that all three organisms have the potential to trigger allergic skin reactions, the option stating "all of the above" is the most comprehensive and accurate answer. This highlights the importance of being aware of various insect bites and stings and their potential effects on allergic individuals.