When making a roller bottle, you need to use appropriate ratios of essential oil and carrier oil, based on the age and skin sensitivity of the intended user. The following guidelines are based on a 10 mL roller bottle.
0-12 months 1-5 drops
1-5 years 5-10 drops
6–11 years 10-20 drops
12 + years 20-45 drops
Seniors 75+ 10-20 drops
Bear in mind that there are always many factors to consider. Some oils are very hot (Oregano, Thyme, Cinnamon, Cassia, for example) and some oils are very mild (Copaiba, Lavender, Frankincense). It's wise to dilute hot oils more. Mild oils may need less dilution. Some people have much more sensitive skin than others. Always use your oils wisely!