Allergies, sneezing and irritated eyes from the air conditioner

Updated 2026-09-04 · reviewed by certified technician

In short Morning sneezing, a blocked nose only at home, watery eyes at the office: the classic pattern of a dirty unit. Spores, mould fragments and fine dust are blown straight into the breathing zone, and the high humidity from a unit that does not dry well feeds dust mites.

A standard filter has limits — Particles of different sizes move through the air.
The filter retains some particles, depending on its type.
A standard filter is not equivalent to HEPA filtration or gas removal.
Particles are symbolic and not to scale.

Man at his desk rubbing irritated eyes under the air conditioner

What is really happening

Irritation and sneezing can have different causes. Inspecting the unit and indoor conditions may help, while persistent symptoms should be discussed with a clinician.

A US EPA study of office buildings found that where coils and pans were not cleaned regularly, eye symptoms and headaches were 60–120% more frequent. The first step is not the antihistamine but a clean unit and humidity between 40 and 60%.

The evidence

What to do

Mechanical pressure cleaning of the evaporator, blower and pan inside a collection cover, then sanitising; filters washed every two weeks; room humidity kept between 40 and 60%; the unit dried on fan mode before winter. No sprays over dirt, no bleach in the unit, no refrigerant "top-ups".

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The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.