I take benadryl (diphenhydramine) everyday about 250mg not at once but during the day for chonic allergies. been doing this for two years will this damage my liver?

No: But it will likely make you less agile and alert. Constipation may also happen for some people.

No, but...: That is really a lot of benadryl (diphenhydramine) and while it will not damage your liver it can have a lot of side effects such as fatigue, dry mouth, constipation and mental slowing. Discuss a change to a non-sedating antihistamine, nasal saline and some nasal steroids with your doctor and try to get off this large dose of benadryl (diphenhydramine). Singulair may also be helpful.