The Belgian aerobiological surveillance network “Airallergy” quickly informs general practitioners, specialists, pharmaceutical firms and the general population of the presence of allergens in the air.
The severity of the allergic reaction to pollen varies from one person to another, because it depends on:
- the immune system of the sensitized person which reacts in different degrees to the allergen
- the type of pollen to which the person is allergic
- the intensity of the pollen season
Seasonal allergic rhinitis or hay fever?
Seasonal allergic rhinitis is an allergy to the pollen of plants (trees, grasses and other herbaceous plants).
Hay fever is a specific allergy to the pollen of grasses. Grasses (Gramineae) are a family of plants which in our regions include some hundred species for which the flowering period is from May to August.
The fungal spores of the moulds which develop on plants may also trigger seasonal allergic rhinitis.
DID YOU KNOW? Substances which can provoke allergic reactions are called “allergens”. But an allergen does not systematically trigger allergy in everyone. For an allergy to be triggered, two conditions are necessary: to be sensitized to an allergen and then be exposed again to this same allergen.
What is an allergic reaction?
An allergy is a hypersensitivity of the immune system.
The organism reacts in an excessive way to a substance that it wrongly considers to be harmful: an allergen.
The pollen of plants, certain foods and cosmetics, house dust mites and animal hairs are normally inoffensive but are potential allergens.
When the allergen comes in contact with the allergic person, the immune system unnecessarily releases histamine and other inflammatory substances, which trigger allergic reactions.
Different types of allergic reactions
There are numerous types of allergies for which the reactions vary according to the type of allergen and the nature of immune response of the allergic person:
- skin rashes (allergies to certain foods, to the sun, insect bites, medications, perfume, cosmetics etc.)
- vomiting and diarrhea (food intolerance)
- running nose, stinging and watery eyes (allergy to pollen, animal hairs, house dust mites).
Most persons allergic to pollen do not react to only one type of pollen but also to the pollen coming from closely related species.
The pollen of the trees of the Betulacae family (birch, hazel, alder and hornbeam) and those of the Fagaceae family (oak, beech and chestnut) contain very similar allergens.
Cross reactions can also occur between pollen and foodstuffs: people who are allergic to birch pollen can show allergic symptoms (itching, swelling of the lips) when eating certain fruits belonging to the Rosaceae family, such as apples, pears, cherries, almonds, apricots, and also when eating hazelnuts and kiwis.