Can psychosomatic disorder cause rash on skin and/or elevated white cell blood count temporary?

It depends: It is a little unusual for a 27 year old male to believe/know he has psychosomatic disorder but perhaps you have been given this diagnosis. In general it means physical symptoms that are caused by mental factors such as stress and anxiety. Some rashes, such as eczema, fall into this category. I do not believe stress/anxiety would cause an elevated white blood cell count. Good wishes:)