Where the allergen actually is, why symptoms run all year rather than seasonally, and an honest account of which avoidance measures the evidence supports — which is fewer than most advice suggests.
Which pollen is airborne in which month, what the weather does to pollen counts, how to treat hay fever in the order that actually works, and why indoor mould is a damp problem rather than a cleaning one.
The symptoms allergy produces, the one feature that most reliably points to it, and the conditions it is most often confused with — colds, non-allergic rhinitis, sinusitis, irritant rashes and intolerance.
Most dry eye is not a shortage of tears but a failure of the oily layer that stops them evaporating — which is why drops alone rarely fix it and lid care usually does more.
Most floaters are harmless and permanent. A sudden new one, a shower of spots, or flashes of light are a different matter and need checking the same day.
How often eyes need testing, who is entitled to a free NHS sight test, what the examination actually involves, and the symptoms that should not wait for the next appointment.
In the UK these lenses can only be supplied through a registered optician, whatever the seller says. What the law requires, why it exists, and what to do if an eye turns painful.
