Infiltration is contraindicated when:

Infiltration is a technique used in local anesthesia where anesthetic is injected into the tissues around a specific site to numb that area. Infiltration is contraindicated in situations where the tissues are inflamed. This is because inflammation can alter the volume and pH of the tissues, which may affect the diffusion of the anesthetic agent. When tissues are inflamed, the blood flow is often increased, resulting in a higher concentration of inflammatory mediators in the area. This can lead to a decreased effectiveness of the anesthetic because inflamed tissue is more acidic, which can prevent the anesthetic from properly ionizing and penetrating the nerve fibers effectively. Therefore, using infiltration in such areas may not achieve the desired anesthesia and can cause discomfort to the patient.

In contrast, hemostasis, the procedure being confined to two adjacent teeth, and treating a child do not inherently contraindicate infiltration. In fact, infiltration may be a suitable technique even in these scenarios but must be assessed on a case-by-case basis, considering the patient's condition and the specific clinical situation.