Alder (Alnus) is among the trees that can open the pollen season. Male flowers, called catkins, develop before the leaves and release wind-borne pollen. For sensitive people, sneezing and a blocked nose can therefore appear in late winter, when many people are not yet thinking about allergy season.
In Italy alder grows mainly in damp environments, along rivers and ditches, near lakes and in some hilly and mountain areas. Species and flowering dates vary from north to south and with altitude. A mild winter can bring flowering forward, while persistent cold and rain can delay it. Seeing a tree nearby is not, however, a measurement of airborne exposure.
The calendar differs by location
In the Po Valley, alder can begin between late January and March; in the Alps and higher Apennines it often starts later. In central and southern Italy, timing depends on the local winter, slope exposure and proximity to water. These are indicative windows rather than a fixed calendar: observations and models can differ from year to year.
pelud.net’s Italian city forecast uses CAMS through Open-Meteo. The alder value is modeled, not measured by a local station in this service, at approximately 11 km resolution. The grid cannot say how many grains are outside your home or account for every river corridor and valley.
Alder and other trees
Alder, birch and hazel belong to related botanical groups. Some people react to several tree pollens during the same period. A positive alder forecast does not prove a diagnosis, and a low forecast does not rule out other plants. The separate birch in Italy article can help explain the succession, but neither calendar replaces testing.
The CAMS model shown here contains six species: alder, birch, grasses, mugwort, olive and ragweed. It does not automatically include cypress, parietaria/urticaceae, plane or every Italian tree. If you have early symptoms while the alder score is low, record the context and discuss it with a professional rather than treating the forecast as a diagnosis.
Possible symptoms
Respiratory allergy symptoms can include repeated sneezing, a runny or blocked nose, itchy nose and eyes, watering and cough. The same combination can have other causes, including infection and irritants. In people with asthma, exposure may coincide with worse breathing, but the score does not measure lung function.
A diary can help: record the date, city, activity, time outdoors, nearby vegetation and symptoms. Compare the diary with the three-day forecast without expecting a perfect match. A doctor can decide whether allergy tests or a seasonal plan are useful. Do not start or stop medicines based only on the site’s value.
Reducing exposure
If winter pollen affects you, check the forecast before activities near rivers, damp parks or flowering trees. On windy days, consider an indoor activity or a shorter stay outdoors. On returning, wash hands and face, change exposed clothes and consider washing your hair before bed. Ventilating at a more suitable time and cleaning with damp cloths can reduce deposited pollen.
These steps do not require removing trees and cannot guarantee symptom-free days. Sunglasses may protect the eyes; for exposed work, ask a doctor or pharmacist what protection is appropriate. People with an asthma plan should follow it and know when to seek help.
Reading an early-season signal
An alder value can rise while the rest of the Italian pollen profile is still quiet. That does not make the day automatically dangerous for everyone, and it does not mean that a later grass or birch season will be equally strong. Look at the individual rows and the weather together. A cold, wet morning, a sheltered riverbank and a windy afternoon can produce different experiences within the same city. The forecast is most useful for deciding whether to shorten an exposed activity and for recognising a pattern in a symptom diary, not for declaring an area pollen-free.
People travelling from the Po Valley to an Alpine resort, or from a coastal city to an inland valley, may encounter a shifted season because altitude and local vegetation change. Check the destination forecast rather than carrying over yesterday's value. If early symptoms appear repeatedly in different places, share those observations with a doctor; alder is only one possible explanation, and the service does not model every Italian tree.
When to seek help
If symptoms persist, disturb sleep or limit school, work or sport, arrange an assessment. Significant breathing difficulty, chest tightness, rapid swelling of the lips or throat, or sudden worsening requires urgent help through local services.
Sources and limits
Read how we calculate risk in Italy, how to protect yourself and birch in Italy. CAMS provides European guidance at approximately 11 km and does not represent every Italian taxon. This article is informational and does not replace medical advice.