Spilanthes acmella Murr. (para-cress or toothache plant) is a medicinal plant of the Compositae family [1]. It is known in Thai as Phak-Kratt Huawaen and has long been used as a traditional medicine for toothache, headache and treatment of asthma, rheumatism, fever, sore throat and haemorrhoids [1–3]. Its root decoction has been used as a laxative and diuretic drug [2, 4]. It is an annual or short-lived herb, spreads in low open places and requires moist soil [5]. Its flowers and leaves have a pungent taste, accompanied with tingling and numbness [2].