Allergy: when a cold lasts a whole season

A cold is an infection. It arrives, peaks and settles, usually inside about a week, and it often brings a sore throat, aches or a raised temperature. It does not usually return on a schedule.

An allergic reaction follows a pattern instead. The nose itches, the eyes water, sneezing arrives in runs, and the same situations bring it back: the bedroom in the morning, the office air conditioning, a friend's cat. It lasts weeks or months rather than days, and it tends to leave you feeling irritated rather than unwell.

From the outside the two can look almost identical, which is why so many people describe months of what they still call a cold. What separates them is the pattern over time, what the lining of the nose looks like under endoscopy, and what a test shows.

Life here is largely indoors and largely air-conditioned. Ducts and filters collect dust, and when a unit is not serviced, mould can develop in the moisture around it. Dust mites do well in cooled bedrooms, in mattresses, sofas and rugs.

Outside, the picture is different from a classic pollen season. Irrigated landscaping keeps grasses and ornamental trees flowering across long stretches of the year, so exposure is spread out rather than concentrated into a few weeks. Sand and construction dust add a mechanical irritant on top, which can inflame a lining that is already reacting.

Pets, indoor plants and regular travel between climates add further variables. Two people on the same street can have the same complaint for entirely different reasons. That is the argument for identifying the trigger rather than assuming it.

A nose that stays blocked changes how you sleep. Breathing shifts to the mouth at night, sleep becomes lighter, and the morning starts with a dry throat and a heavy head. In children the same thing often shows as snoring, restlessness or difficulty settling.

The lining of the nose continues into the sinuses and connects to the middle ear through the eustachian tube. Swelling in one area can affect drainage and ventilation in the others, which is one reason repeated sinus symptoms and blocked-feeling ears often appear alongside allergy. A reduced sense of smell belongs to the same picture.

None of this necessarily means something is wrong beyond the allergy itself. It means the symptom has a source, and that source can often be identified in a single appointment.

Testing beats guessing. A positive result shows that the immune system recognises a substance, which is called sensitisation. It becomes clinically relevant when it lines up with your history and with what the nasal lining is doing.

This is why the consultation is not only the test. The endoscopic view, the timing of your symptoms and the rooms you spend your days in all feed into how the result is read. A strong reaction to something you rarely meet matters less than a modest reaction to what is in your bedroom.

It also works the other way. Symptoms with negative allergy tests are not imagined; non-allergic rhinitis, structural narrowing, medication effects and sinus inflammation all produce a similar picture. In that case the search continues rather than stops.