Scientific laws are considered established and universally applicable (to certain class of things or phenomenon under appropriate conditions) but not necessarily definitive. Also called laws of science.
Afflictions of the respiratory system include irritation and infection of the ears, nose and throat. Respiratory problems also may involve congestion, which can be decreased by inhaling rosemary (especially the verbenone type), hyssop (use var. decumbens only), tea tree, eucalyptus, lavender or peppermint.
How to use essential oils for a cold: Because colds are respiratory infections, inhalation is the logical choice for using essential oils. An ultrasonic diffuser is a great choice because the humidity from the mist can help with dry respiratory passages.