Seasonal allergic rhinitis affects millions of people around the world.

Seasonal allergies cause symptoms such as allergic conjunctivitis (itchy, red and watery eyes), allergic rhinitis (sneezing, blocked or runny nose, swelling and itching in the oral area) psychological symptoms (fatigue, irritability, poor sleep, negative effect on concentration and performance) and allergic asthma with a dry cough and shortness of breath.

Seasonal allergens include:

Pollen

Pollens are suspended in the air on sunny and warm days, they can be carried by the wind over several kilometers. The amount of pollen ion the atmosphere is lower on rainy days as well as on cold and humid days.

Pollens responsible for respiratory allergies come from three categories:

Trees

Tree pollen which can trigger allergies include:

• the Betulaceae family (birch)
• the Fagaceum family (beech, oak)
• the Oleacceae family (ash, olive tree)
• the Cupressaceae family (cypress, juniper, cedar)

Their pollination period is spread over several months (from March to September in the Northern hemisphere) and varies from one species to another.

Grasses

The Poaceae (grass) family includes more than 12,000 différent species. Grasses are found in gardens, lawns, forests as well as on water or on rocks. Even a tiny concentration of grass pollen is enough to trigger an allergic reaction.

Fodder and cereal grasses which can trigger allergies include: dactylic (cocksfoot or orchard grass), timothy, sweet vernal, ryegrass and bluegrass. In the Northern hemisphere their pollination period extends from March to September with peaks in May, June and July.

Weeds

Species from the herbaceous family have soft and supple stems. Their pollens, which are small and light, can remain suspended in the atmosphere for a long period of time and can be carried over long distances.

Herbaceous weeds which can trigger an allergic reaction include: mugwort, nettle, lamb’s quarters, ragweed, sage, Russian thistle… Aromatic plants such as lemongrass, tarragon, and wormwood are part of the same family (Asteraceae).

Their pollination season in the Northern hemisphere goes from March to September with peaks in July, August and September.

Mould

Fungi can be found both outdoors (fallen leaves, compost, grasses, etc.) and indoors in damp areas (bathroom, kitchen, etc.). The spores released by the fungi can be carried by wind and dew.

The microscopic size of fungi spores, which ranges from 3 to 10µm), enables them to easily penetrate the respiratory tract.

Mould can trigger respiratory allergies, both on a seasonal and perennial basis, such as allergic rhinitis, conjunctivitis and asthma.

The most common moulds which trigger allergic reactions are:

• alternaria alternate (indoor and outdoor mold)
• penicillium and cladosporium (which are present outdoors but predominant indoors)
• aspergillus: a type of mold which can trigger immediate reactions (sneezing, cough, skin rash) as well as more critical reactions such as pulmonary aspergillosis (pulmonary disease)