Which of the following statements about antihistamines is true?

Antihistamines are a class of medications that block the action of histamine, a substance in the body that is involved in allergic reactions. While they are predominantly known for their role in treating allergies, they can also be used in the context of anxiety associated with pain. This is primarily due to the sedative properties of some antihistamines, which can help alleviate the feelings of anxiety that may accompany pain. This ability to reduce anxiety is often utilized in clinical settings, especially when treating patients who experience anxiety as a response to pain conditions.

The other statements do not accurately reflect the uses of antihistamines. They are not limited to treating allergic reactions; their effects on sedation and anxiety make them versatile in managing various conditions beyond allergies. While they are not primarily classified as pain relievers, their sedative properties can help address the discomfort linked to pain, indirectly benefiting those who experience anxiety related to pain. Hence, the statement that they are used for anxiety associated with pain accurately represents one of their potential applications in clinical practice.