Pollen grains contain potent allergens which can cause hay fever, asthma attacks and conjunctivitis. As pollen comes from trees, grass and weeds, most exposure occurs outdoors. However, pollen is also a component of household dust, so you may also find yourself reacting to pollen indoors. Pollen is probably one of the most difficult allergens to avoid because it is very mobile and can hover in the air for long periods of time.
Pollen grains contain proteins that cause the immune system in an allergic person to over-react. Exposure to the allergen proteins causes the production of antibodies known as Immunoglobulin E, which in turn trigger a release of histamine from mast cells, a type of immune cell. It is histamine that leads to symptoms of allergy like redness, sneezing, swelling and runny nose. A skin prick test, in which you are exposed to various pollen allergens, will confirm whether you have an allergy. Pollen grains that cause allergies are between 10 and 40 microns in size with most being between 20 and 35 microns. Some pollen grains fragment into particles around one micron in size. Pollen can travel a long way through the air, which is why allergies occur in cities and pollen is found high in the atmosphere and miles out to sea.
1) Hay fever, also known as seasonal rhinitis. Symptoms include:
2) Asthma symptoms include:
3) Conjunctivitis (inflammation of the conjunctiva, which are the membranes lining the inside of the eyelids) symptoms include:
The size and shape of pollen grains favour their deposition on the conjunctiva.
In the United Kingdom, the most common allergens are (in order):
1. House dust mite
2. Grass pollen
3. Cat Dander
4. Tree pollen
Warm airlifts pollen high into the atmosphere during the day. When air cools down, as dusk falls, pollen starts to descend. You may well be exposed to one of these ‘pollen showers’ in the early hours of the morning if you sleep with a window open. Helpful tips are to:
A dust mask filters out pollen grains larger than 5 microns and may be useful sometimes. The main problem with dust masks are:
a) they only filter out large particle pollution
b) that they restrict your breathing
The better the filter media of the dust mask is, the more restricted your breathing will be. The result is that you will breathe the smallest and most harmful pollution deeper into your lungs than you would without wearing a dust mask. For that reason, we do not recommend using dust masks when cycling. Alternatively, use a scarf over your nose or smear a little Vaseline inside your nostrils to trap some of the pollen grains.
Try these tips to reduce exposure:
Tree, grass and weed pollens contain hay fever allergens. These have small, insignificant flowers which do not attract insects. Generally, the brightly coloured flowers of insect-pollinated garden plants like roses or wild plants, including poppies, do not cause hay fever. The tiny grains of pollen (ranging in size from 0.25 to 100 microns) readily become airborne and are capable of travelling through the air many miles from their source.
Check the lists below to see which pollens might be causing your hay fever:
| Trees: | Ash Birch Cedar Chestnut Cypress Elder Elm Hazel Oak Poplar Sycamore Walnut Willow |
| Grass: | Dogstail Fescue Foxtail Meadow Oat Rye Timothy Vernal |
| Weeds: | Dock Mugwort Nettle Plantain Ragweed Sorrel Wall pellitory |
Grass releases pollen from around 7 in the morning and later in the day if the ground is damp. Some grass species don't release their pollen until the afternoon.
Birch trees release their pollen between noon and 6 pm.