Rosmarinic acid (α-o-caffeoyl-3,4-dihydroxyphenyllactic acid; RA) is a naturally occurring hydroxylated compound commonly found in species of the subfamily Nepetoideae of the Lamiaceae and Boraginaceae, such as Rosmarinus officinalis, Salvia officinalis, and Perilla frutescens. RA is biosynthesized from the amino acids L-phenylalanine and L-tyrosine by eight enzymes that include phenylalanine ammonia lyase and cinnamic acid 4-hydroxylase. Recently, RA and its derivatives have attracted interest for their biological activities, which include anti-inflammatory, anti-oxidant, anti-angiogenic, anti-tumor, and anti-microbial functions. Clinically, RA attenuates T cell receptor-mediated signaling, attenuates allergic diseases like allergic rhinitis and asthma, and 2,4-dinitrofluorobenzene-induced atopic dermatitis-like symptoms, protects from neurotoxicity, and slows the development of Alzheimer's disease. Rosmarinic Acid seems to be able to suppress 5-lipoxygenase and 5-HETE synthesis (a pro-inflammatory compound in the omega-6 metabolic chain). Rosmarinic acid appeared to be effective in suppressing allergies in a dose-dependent manner, with 30% of the placebo group reporting symptom relief compared to 55.6% of the 50mg group and 70% of the 200mg group.