Topical methyl salicylate and topical capsaicin have also been used. Desensitization of TRPV1 is thought to underlie the paradoxical analgesic effect of capsaicin. The TRPV1 agonist capsaicin, found in chili peppers, has been indicated to relieve neuropathic pain. Like in thermal nociceptors, TRPV1 can detect chemicals like capsaicin and spider toxins. Phenolic hydroxide and amide moieties appear to be vital for inducing capsaicin responses. The solvent is then evaporated, and the remaining waxlike resin is the oleoresin capsaicin. Because this receptor responds to both capsaicin and heat, chili peppers are sensed as hot. Eosinophils in response to capsaicin, can trigger further sensory sensitization to the molecule. Aquagenic urticaria is treated with capsaicin (Zostrix) administered to the chafed skin. It is common for people to experience pleasurable and even euphoric effects from ingesting capsaicin. The latex of "Euphorbia resinifera" contains Resiniferatoxin, an ultra potent capsaicin analog. Capsaicin and dihydrocapsaicin (both 16.0 million SHU) are the most pungent capsaicinoids. Novel preparations containing higher capsaicin concentration (up to 10%) are under clinical trials. The thermoreceptor reacting to capsaicin and other heat producing chemicals is known as TRVP1. Upon prolonged exposure to capsaicin, TRPV1 activity decreases, a phenomenon called "desensitization".