How do i treat hives from tegaderm picc dressing?

Rash?: I suspect that your problem is more a contact allergy rash to the glue in the tape than really hives (which are raised welts). You cannot stop the rash as long as you are using the tape. However if you are no longer using it, then topical Hydrocortisone cream several times a day may control it.

Contact Dermatitis: There are two forms of contact dermatitis. Irritant contact dermatitis occurs at the site of application of toxic chemical or substance which is directly noxious to skin. The second, allergic contact dermatitis, is an itchy rash that occurs only in people who have developed an allergic sensitivity to that particular chemical or substance. Treatment is avoidance or strong topical steroids.