One of the most difficult tasks in eldercare is in the area of bathing. Often people with dementia stop bathing, and resist being bathed. Besides the resistance, it is also a challenge because this means that family members may have to step in, causing discomfort and embarassment. It crosses a lot of psychological and cultural lines.
One thing to remember is that when people are resisting bathing, they may be feeling frightened of the process, assaulted, or embarrassed. If there is a history of being sexual abused, someone bathing them can trigger memories associated with the abuse. Before and after getting into a shower, the individual can feel cold. Being naked can also make someone feel very vulnerable, even if they do not know why, or cannot label or describe what they are experiencing.
Some additional help can be found at http://www.bathingwithoutabattle.unc.edu/SideFrame_MainPage.htm
They have a text they have developed, called Bathing Without A Battle.