Fleas are insects that form the order Siphonaptera. They are wingless, with mouthparts adapted for piercing skin and sucking blood. Fleas are external parasites, living by hematophagy off the blood of mammals and birds.

3,4-Methylenedioxy-N-hydroxy-N-methylamphetamine (MDHMA; FLEA) is an entactogen, psychedelic, and stimulant of the phenethylamine and amphetamine chemical classes. It is the N-hydroxy homologue of MDMA ("Ecstasy"), and the N-methyl homologue of MDOH. MDHMA was first synthesized and assayed by Alexander Shulgin. In his book PiHKAL (Phenethylamines i Have Known And Loved), Shulgin listed the dosage range as 100–160 mg, and the duration as approximately 4–8 hours. He describes MDHMA as causing entactogenic and open MDMA-like effects, easing communication, and increasing appreciation of the senses.