Pure Thuja Essential Oil (Thuja occidentalis) Thuja Oil is used for bacterial skin infections and cold sores. It is also used for painful conditions. Some people use Thuja Oil to loosen phlegm (as an expectorant), Sore throat (tonsillitis), Nasal swelling (sinusitis) to boost the immune system (as an immunostimulant) and to increase urine flow (as a diuretic). It has also been used to cause abortions. Thuja Oil is sometimes applied directly to the skin for joint pain and muscle pain. Thuja Oil is also used for skin diseases, warts, and as an insect repellent. Thuja Oil is used for respiratory tract infections bacterial skin infections, cold sore, osteoarthritis, trigeminal neuralgia, increase urine flow, as an expectorant, to boost the immune.