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pollen s'envolant

Pollens are part of plants’ reproductive organs.

Their mobility is due to either wind or insects and can cover kilometers. They are present everywhere, even in large cities.


Each type of plant (tree, gramineae, cereal or grass) has a distinct pollen and specific pollination period (influenced of course by climate and weather)

The dates during which allergic symptoms appear give an indication as to which pollens are causing them.


Pollens which cause geatest allergic symptoms are the smaller ones transported in the air.

They enter easily into the respiratory system, through the nasal cavity and bronchial tree, and agglutinate against nasal and bronchial mucous membranes, as well as in the eyes.

  • In Switzerland, trees tend to pollinate from end of January to end of April. Hazeltree, Aldertree, Birchtree and Ashtree are the most allergenic. It is frequent to be allergic to the three principal trees (first 3 in our list) because they are part of the same species (betulacées) and induce crossed reactions.
  • gramineae (grass) and cereals (wheat,oat, barley) pollinate in May and June. It is not vital to make precise distinctions between different species of gramineae and cereals in terms of allergy symptoms, as most of these pollens are alike and cross-react amongst themselves.
  • Herbaceous plants (artemisia, plantain) pollinate in August up to early October. Allergy to these last plants is less frequent.

Pollinosis, or allergy to pollen, is also often called “hay fever”.

For those who have a tendency to develop allergies, being repeatedly exposed year after year to pollens causes to maintain pollinosis and stimulate the immune system. Between pollination periods, the immune system is freed from stimulation and the reaction abides.

Accordingly, symptoms tend to increase each year, and can start at any age.

  • Nose: allergic rhinitis with pruritus, sneezing, rhinorrhea and severe nasal obstruction
  • Pharynx: itching, irritation
  • Bronchial tree/ respiratory system : seasonal asthma (=breathing difficulties, mucus and bronchial inflammation)
  • Eyes: allergic conjunctivitis with pruritus, redness, tears, and secretions

Allergy to Pollen diagnosis

Allergist can determine diagnosis by:

  1. Anamnesis (patient’s history of reactions and symptoms periodicity)
  2. Skin prick-tests (standard), eventually intra-dermal (IDR)
  3. Blood test for measure of  specific IgE
  4. Lung function (spirometry) to detect asthma


The MD Allergy specialist will suggest various treatments depending on severity and chronicity of symptoms:
  • Medication: a number of drugs will relieve hay fever symptoms during pollination
    • mostly eyewash, nasal spray, inhaler, tablets
    • usual molecules are anti-histaminic, cromoglycat, anti-leucotrien, bronchodilatators and corticosteroids
  • Cure: desensitization (allergic vaccination) following an annual or seasonal protocol.


Oral Allergy Syndrome (OAS) is mentioned here due to frequent crossed-reactivity between fruits and pollen (i.e. apple-birch tree), that typically develops in hay fever patients.

Another term for this syndrome is “pollen-food allergy”.

The allergic reactions in the mouth occur in response to eating certain (usually fresh) fruit, nuts and vegetables. Symptoms are pruritus, discomfort in the mouth or throat, sometimes evolving towards asthma or fainting.

Crossed-reactions result from common antigens found both in pollens and fruit. These antigens stimulate sensitized patients’ immune system.

For this reason, patients suffering from hay fever frequently also report allergic reactions to fruit, sometimes a far as anaphylactic shock. The consult with the allergist will clarify diagnosis and provide advice and appropriate medication in case of reaction.

It is interesting to note that after desensitising a patient against pollens, OAS symptoms may improve.