Fatty acids that must normally be present in the diet of certain animals, including humans. Essential fatty acids belong to the omega-6 and omega-3 series of polyunsaturated fatty acids, the parent compounds of which are linoleic acid (n-6) and α‎-linolenic acid (n-3); all possess double bonds at the same two positions along their hydrocarbon chain (counting positions from the methyl end) and so can act as precursors of eicosanoids, including the prostaglandins. Deficiency of essential fatty acids can cause dermatosis, weight loss, irregular oestrus, etc. Recommendations for dietary intake of essential fatty acids vary, but both n-3 and n-6 acids should be consumed, ideally in roughly the same amounts.