Can triamcinolone acetonide be used for poison oak and poison ivy?

Yes: Topical steroids are effective for these conditions. More severe cases may require stronger topical preparations or oral corticosteroids.

Depends on area : Poison ivy (in eastern us), oak (in western us), sumac (in eastern us) are 3 species in the genus toxicodendron or rhus which all produce urushiol oil, the substance that in sensitive individuals produces contact dermatitis. Topical triamcinolone can be used if the area of affected skin is less that a few square inches. If area larger may require oral corticosteroid, e.g. Prednisone.

Yes: Any topical steroid cream can be used for any type of contact dermatitis. Poison oak and ivy, however, cause extremely potent reactions, that may not respond well to topical therapy, and need to be treated with steroids taken by mouth. If you're using the steroid cream twice daily and can tell that the rash is worsening or spreading, you need to see your physician.