While not necessarily dangerous they can cause health problems if allowed to enter and multiply in a friendly environment. Olfactory bulb and nerves. Taste fibers on the tongue and buccal lining. This is well known but not well studied or tested. A birds olfactory senses are similiar to bats and mice but are not used for the same purpose.
Birds prefer little or no unusual odors present.
The stronger the odor the stronger the response. Dr. T's repellents produce the following reactions, none of which are destructive or permanent. Increased heart rate. Immeditate respiratory effect. This in turn causes a blood gas exchange problem which increases respiration and heart rate.