What is one of the conditions treated by antihistamines due to their anticholinergic effects?

Antihistamines are primarily known for their ability to alleviate symptoms associated with allergic reactions, such as those seen in allergic rhinitis. However, they are also effective in treating motion sickness because of their anticholinergic properties. These anticholinergic effects help reduce the activity of the vestibular system, which is involved in balancing and spatial orientation, making them useful for preventing nausea and dizziness associated with motion-related conditions.

In contrast, while antihistamines can be helpful in some contexts of asthma treatment, their primary role is not focused on direct treatment of asthma but rather on managing allergic symptoms that can exacerbate it. Pneumonia is a bacterial infection that typically requires antibiotics rather than antihistamines for treatment. Therefore, the application of antihistamines in the context of motion sickness highlights their versatility due to these anticholinergic effects, distinguishing this condition from the others listed.