Below Willow is with regard to Eucalyptus. So you can gather from this that caution is necessary!

If consumed internally at low dosage as a flavouring component or in pharmaceutical products at the recommended rate, cineole based 'oil of eucalyptus' is safe for adults. However, in its pure form it is poisonous according to dosage.
The probable lethal dose of pure eucalyptus oil for an adult is in the range of 0.05 mL to 0.5 mL/per kg of body weight.[17] Because of their low body weight, children are more vulnerable to poisons. Severe poisoning has occurred in children after ingestion of 4 mL to 5 mL of eucalyptus oil.[18][19]