Overcooking can destroy fatty acids. Improper storage or a suboptimal amount of antioxidants in dry food may result in rancidity and a subsequent deficiency in fatty acids. EPA is the workhorse of the omega-3 fatty acids and is incorporated into the cell membrane. LA can be converted into GLA, but not in the skin. However, DGLA can be made from GLA in the skin.
LA is important because in optimizes water permeability in the skin.
AA, on the other hand, in increased amounts, is the troublemaker among the fatty acids. It is important to realize that although the ratios may be a guideline, the actual concentration of EPA in the omega-3's is what's most important. Fat may contain fatty acids, but in extremely varying quantities. For example, beef fat will have a very low percentage of fatty acids, whereas sunflower oil and fish oil will have much larger percentages. Essential fatty acids are found in different quantities in many plants and cold water fish.