Capsaicin is a topical analgesic that is FDA approved for the treatment of neuropathic pain associated with postherpetic neuralgia. Capsaicin is most often used as a topical analgesic and exists in many formulations of cream, liquid, and patch preparations of various strengths; however, it may also be found in some dietary supplements. Capsaicin is a naturally-occurring botanical irritant in chili peppers, synthetically derived for pharmaceutical formulations. Capsaicin is an agonist for the transient receptor potential vanilloid I receptor (TRPVI), which is an ion channel-receptor complex expressed on nociceptive nerve fibers in the skin. Common adverse reactions include erythema, rash, pruritus, nausea.

Davasaicin is a synthetic derivative of capsaicin, developed at the Korea Research Institute of Chemical Technology. Davasaicin possesses very potent analgesic activity, demonstrated in several animal models, such as phenylbenzoquinone-induced writhing test, tail-flick test in mice and adjuvant arthritic flexion test in rats. When administered topically, davasaicin has an antipruritic effect in the mouse model.

Vanillin (4-hydroxy-3-methoxybenzaldehyde), a pleasant smelling organic aromatic compound, is widely used as a flavoring additive in food, beverage, cosmetic and drug industries. It is reported to cross the blood brain barrier and also displayed antioxidant and neuroprotective activities. Vanillin is a natural substance widely found in many plant species and often used in beverages, foods, cosmetics, and pharmaceutical products. Antioxidant and anticancer potential have been described for this compound. Vanillin has been classified as a bioantimutagen and is able to inhibit mutagenesis induced by chemical and physical mutagens in various cell systems. Vanillin, a selective agonist of TRPV1, has been shown to attenuate i.c.v. STZ and AlCl3+d-galactose induced experimental Alzheime's disease (AD).