On an ownership or rental basis, operate farms, ranches, greenhouses, nurseries, timber tracts, or other agricultural production establishments which produce crops, horticultural specialties, livestock, poultry, finfish, shellfish, or animal specialties. Include operators of cotton gins, packing houses, and other post-harvest operations. May plant, cultivate, harvest, perform post-harvest activities, and market crops and livestock; may hire, train, and supervise farm workers or supervise a farm labor contractor; may prepare cost, production, and other records. May maintain and operate machinery and perform physical work. [SOC] See "Farming, growing up on a farm, and haematological cancer mortality." One of the hypotheses is that exposure to viruses through contact with farm animals increases risk. [PMID 21795741] Causes of allergic contact dermatitis include poison ivy and some carbamates and fungicides. Cow dander and grain dusts can cause contact urticaria in farmers.