Latin name: Poaceae (family)
Plant description: Long, slender leaves with green, spikey flower-heads (pannicles). Grasses are usually between 5 Ė 100 cms in height when in full flower. The pollen is produced on the tiny anthers which hang down from the pannicles. The anthers may be yellow, white, green or purplish in colour.
Distribution: worldwide distribution. Approximately 150 different species occur in the UK (not including ornamental grass species).
Allergenicity and other health impacts: Highly allergenic, affecting approximately 95% of hay fever sufferers and can also induce asthma attacks. Grass can produce a rash if brushed on bare skin and the sap can become airborne and induce allergy (e.g. when mowing the lawn).
Season: Depending on the weather, the grass pollen season can start in April or May with low levels initially. The south of the country can start much earlier than the north. Moderate and high levels donít usually occur until late May or early June. The peak season is usually in mid-June and the season usually goes into decline in mid-July but there can be grass pollen airborne until the beginning of September.
Daily pattern of release: Grass pollen levels are highest on warm, dry days. On these days, the pollen is at its worst in the first half of the morning and again from late afternoon and into the evening.