I Developed A Rash Just Around My Armpit Area And

I developed a rash just around my armpit area and chest about a month ago. red blister like bumps. very itchy... this spreading slowly under my breast area and each day spreading down stomach to just above pelvic are. some on only one knuckle on right pointer finder...but has eased off. spreading onto hip area...and some on upper arm above elbow joint area. Very itchy throughout day, but shower in morning and evening brings welting and blistering out more. My son's girlfriend whom lives in our basement suite has the same symptoms however she's not as itchy. We both have dairy (cow) allergies and are allergic to cedar. We live on a parcel of land that has a lot of cedar trees her in Lower mainland of British Columbia Canada
Any suggestion. My doctor thought Eczema but now doesn't with both us ladies having similar time of symptoms