Scanning electron micrograph (SEM) of pollen grains from the common oak flower Quercus robur. Oak trees flower in May/June producing copious quantiies of pollen, which is dispersed by the wind. Oak pollen is a major cause of hay fever (medical term Allergic rhinitis and pollenosis). Sufferers produce an antibody, immunoglobin E (IgE), which attaches to cells in the nose & eyes. It reacts with inhaled pollen causing the release of various chemicals including histamine. Histamine causes the mucous membranes of the nose, eyes & throat to swell & become inflamed, bringing on the hay fever attack. Mag: X1200 (10x8).