Plain English Meaning
Pills or liquids you swallow to relieve a stuffy nose or blocked sinuses. Pilots are warned about them because they can cause side effects that make flying unsafe.
Full Definition
Medications taken by mouth that reduce swelling of the nasal and sinus tissues by constricting blood vessels in those areas. In aviation medicine they are generally discouraged because they can produce side effects such as drowsiness, dizziness, blurred vision, or impaired judgment that affect a pilot's fitness to fly.
Context Anchor
Seen in aeromedical discussions of colds, allergies, sinus blockage, and ear pressure during climbs and descents.
Derivation
From Latin 'de-' (reverse, remove) and 'congestus' (crowded, packed together). A decongestant literally 'un-crowds' swollen tissues. 'Oral' simply means taken by mouth, distinguishing these from sprays or drops.
Why Pilots Care
Side effects such as drowsiness or rebound congestion can impair alertness and the ability to equalize pressure changes during .