Why To Dilute
I always dilute essential oils when using them with dogs, because they are potent. A tiny amount has strong effects, so there is no reason to use undiluted oils. Just as with aspirins, you don't use five when one will do the trick. What's more, aromatics work better when diluted. Their molecules "curl up" when they are too densely packed, and stretch out to look for each other when in low concentration. Diluted essential oils are more easily absorbed by the body, so no energy is wasted on excretion, and you reduce the possibility of the irritation or sensitization.
But the main reason I dilute is because the dogs have shown me they prefer it that way. I have seen dogs, who have been previously traumatized by smelling undiluted essential oils, run out of the room at the sight of one of those evil little glass bottles. The more sensitive the dog, the more important it is to dilute well. Before we leave this question open, open a bottle of essential oil and smell it. Now imagine that smell 100,000 times more powerful. Do you feel overwhelmed at the thought? Well, a dog's sense of smell is at least that much more sensitive than yours, it could be as much as 1,000,000 times more so....
How to dilute essential oils
Essential oils should be diluted in a carrier oil. Pour the carrier oil into a small bottle . A five or ten milliliter glass bottle works best, available from most aromatherapy suppliers. The bottle should have a screw top cap, to keep the diluted oil fresh.
Label the bottle with the names of the essential oil and carrier oil and the dilution level. Wrap a piece of clear sticky tape around the label so that, when oily, it doesn't slip off. If stored in a cool dark place, the diluted oil will stay fresh for about three months.
Dilute each essential oil/hydrosol separately. Do not blend. Your dog needs the freedom to interact individually with each extract. If you mix the oils, your dog is likely to refuse the blend when he goes off only one of the oils. Or, if he really is desperate , he may continue to take the blend just for the one oil he needs, increasing the risk of sensitization or irritation.
Rates of Dilution, essential oil
Physical problems 1-3 drops of essential oil in 5 ml/1 teaspoon of carrier oil.
Emotional problems/trauma 1-2 drops essential oil in 10ml/2 tsp of carrier oil, or use hydrosol.
The more sensitive or delicate the dog, the higher the dilution should be (less essential oil more carrier) For puppies and the nervous or highly strung, use only hydrosols.
Reference:The Aromatic Dog : Nayana Morag