Doc perscribed triamcinolone cream 0.1% for up to one Month. Contact dermatitis all over body. Is it safe to use that much for that long?

Possibly safe but... If you need to cover the entire body with this cream, you may as well be put on oral prednisone. You should consult a dermatologist however to find out what is causing the problem since this may cause systemic effects , just like systemic cortisone, when used for long. Avoid using it on the face whenever possible.