fineexampl said:
I've never heard about basil being harmful in any way.
Apparently only in large doses
http://www.e2121.com/food_db/viewherb.php3?viewid=125&setlang=
Toxic or Side Effects:
There is little available literature on the toxicity of basil. However, Ocimum basilicum, the species that appears to be used the most medicinally and the one for which the most analysis has been done, contains several potentially dangerous compounds. Some of these compounds are: safrole, rutin, caffeic acid, tryptophan, and quercetin.
Acute bovine pulmonary emphysema (ABPE), a respiratory disease in cattle, is caused by absorbed metabolites of tryptophan. Usually, ABPE occurs in cattle over 2-3yrs of age that are suddenly moved onto lush pasture. Tryptophan is toxic at a dose of 0.25-0.35 g/kg body weight. Whether or not a dose of basil could cause ABPE is not known.
P-coumaric acid and caffeic acid can inhibit digestion of plant cell walls in ruminants, because of their antimicrobial activity. When these acids are metabolized by rumen microbes, benzoic acid, 3-phenyl-propionic acid (PPA), and cinnamic acid may be formed. When these compounds are detoxified, hippuric acid is formed. PPA can decrease metabolic efficiency. Detoxifying the compounds costs the animal nitrogen, which also can decrease productivity.
Quercetin (a flavanoid) may be a cocarcinogen in bracken fern (Pteridium aquilinum). It has been suggested that it may interact with Bovine papilloma virus type 4, leading to malignant epithelial papillomas in the upper alimentary tract. Adverse effects from quercetin in Ocimum spp., when used to treat animals, is not known.
Safrole, which was used to flavor sodas, was banned as a food additive in the U.S. It has been shown to cause cancer in rats. Oil of Ocimum also contains d-limonene, which has anticarcinogenic properties.