you have glaucoma or urinary hesitancy, these may become worse.

Antihistamines like you are using are generally considered mild, but they do
cause drying of mucus membranes, and may dry you out some. (this can make
you prone to upper respiratory infections/colds). Or if you have dry eye or
Sjogrens's it would be a concern. Since you are sleeping, blurred vision is not a major issue either. However, you may have morning grogginess depending on dose.

But I wouldn't worry much, if it works for you... I don't know of any addicting
issues with it.