Unlike omega-3 and omega-6, omega-9s are not considered essential. This is because they can be produced within the body, and because they do not participate in the synthesis of eicosanoids. The most common omega-9 fatty acids are oleic acid (olive oil and macadamia oil) and erucic acid (rapeseed and mustard seed oil).
Olive oil is made up of about 85% oleic acid and has gained lots of popularity as part of a healthy diet. This in part to the high omega-9 levels, low omega-6 levels and a variety of beneficial polyphenols.
Other omega fatty acids include omega-5s (nutmeg), and omega-7s (sea buckthorn oil). These fatty acids are not considered essential, and there appears to be little literature as to their benefits. However, preliminary research suggest that sea buckthorn may be beneficial for atopic dermatitis.