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.
The concentrations of tea tree oil used in studies have varied depending on the medical condition. For instance, a 5% tea tree oil gel might be used for acne, while a 10% or higher tea tree oil cream might be used for athlete's foot. 100% tea tree oil solution has been used with toenail fungus. If you use tea tree oil, follow the instructions on the label or get advice from your doctor.