A lot of the plants like that have aromatic essential oils as the part that gives them scent, containing things like D-menthone, carvone, chavicol, linalool, and various other terpenes, and other bits and pieces.
It might well be a bad idea actually, as the essential oils are extremely concentrated, and some are toxic when taken internally.
Some ones definately to avoid, are sage oil, as it contains around 90% alpha and beta thujones, which are found mainly in plants of the wormwood (artemesia) genus, and are severely hepatotoxic in anything but milligram amounts, also avoid clove oil, as this contains large amounts of eugenol and methyleugenol, which have recently been thought to be carcinogenic, and can lower blood sugar levels, and mess up the liver and renal tubules, also avoid basil oil, as this contains eugenol compounds, oil of pepper, which can be irritant, due to its piperine content, and lastly, definately avoid nutmeg oil, due to the hepatotoxic safrole content, and myristicin, which although not TOO friendly to the liver, will cause intoxication like that of primary amine type substited psychadelic amphetamines such as MDA or MDE (potententially for a few days).
Parseley seed oil, fennel seed oil, and similar types of things are best saved for synthesis of the likes of various..sympathomimetic compounds, as mentioned above IMHO, rather than an addition to your salad. (theoretically of course)