From my understanding, the total number of oils is not the safety concern, it’s the total amount of EOs used (the final dilution) that matters. While there are various dilution guidelines, these are the most recent recommendations from aromatherapists I respect. Products that cover large portions of your body and sit on the skin for long periods of time (like lotions) need to be diluted more (1-2% depending on the strength of the EOs used). Products that don’t sit on the skin for long (like body washes) can be diluted less (around 5-10%, again depending on the strength of the oils used). Products that cover larger portions of skin (salve with EOs) should be more diluted (2-3%) compared to products that cover smaller portions of skin (roller bottle spot applications) which can be less diluted (5%). Age and health will also be a factor in dilution amounts. Children and the elderly need their EOs to be diluted more as their livers are slower at metabolizing EO chemicals than a healthy teenager or adult liver. Dilution also depends on the strength of the oil. For example, cinnamon bark requires more dilution than cinnamon leaf. Does this make sense? A lot of EO books (like this one) give recommendations and guidelines for this sort of thing.
Lavender is said to ease tension and induce relaxation. In studies done by Britain’s University of Southampton, they found that participants who diffused lavender oil at night ranked their sleep an average of 20% better than the placebo group. Newer research done by Wesleyan University confirms these findings. When combined with roman chamomile it delivers a knock-out punch for insomnia.
You need a cool-air diffuser. These diffusers usually require a small amount of distilled water to be added along with essential oils. Note: Cold air diffusers ranges vary, with most around 250 feet. So if you are trying to diffuse your bedroom and living room, most likely you will need two diffusers. This one is my favorite for the money and size/features.