Variously called Death Day, Decision day, and a number of other less kind words, D-Day was the day that the Allies began the big push from the coast of France all the way to the heart of Germany, ending WWII.
More importantly when it comes to cystic acne, tea tree oil can be harmful to your skin when applied in high concentrations. Some individuals have reported severe skin irritation and allergic dermatitis after applying too much tea tree oil, or applying the proper dose too frequently.
In fact, tea tree oil may be a better alternative to conventional skin treatments. Tea tree oil is an excellent treatment for acne. One study found tea tree oil to be just as effective as benzoyl peroxide, but without the negative side effects like redness and peeling.