Why can't people over 65 take Benadryl?

I've heard that individuals over the age of 65 are advised against taking Benadryl. Could you please elaborate on the reasons behind this recommendation? Is it due to potential side effects that may be more severe in older adults? Or are there specific health conditions that are more prevalent in this age group that may interact negatively with Benadryl? Understanding these factors would help me make informed decisions about medication use for myself and my loved ones.