Phenethylamine is produced by a wide range of species throughout the plant and animal kingdoms, including humans it is also produced by certain fungi and bacteria (genera: Lactobacillus, Clostridium, Pseudomonas and the family Enterobacteriaceae) and acts as a potent antimicrobial against certain pathogenic strains of Escherichia coli (e.g., the O157:H7 strain) at sufficient concentrations.

The class of substituted phenethylamines includes all substituted amphetamines, and substituted methylenedioxyphenethylamines (MDxx), and contains many drugs which act as empathogens, stimulants, psychedelics, anorectics, bronchodilators, decongestants, and/or antidepressants, among others.

Phenethylamines, or more properly, substituted phenethylamines, are the group of phenethylamine derivatives that contain phenethylamine as a 'backbone' in other words, this chemical class includes derivative compounds that are formed by replacing one or more hydrogen atoms in the phenethylamine core structure with substituents. Some authors postulated its role in people's falling-in-love without substantiating it with any direct evidence. This means that for significant concentrations to reach the brain, the dosage must be higher than for other methods of administration. Phenethylamine is sold as a dietary supplement for purported mood and weight loss-related therapeutic benefits however, in orally ingested phenethylamine, a significant amount is metabolized in the small intestine by monoamine oxidase B (MAO-B) and then aldehyde dehydrogenase (ALDH), which converts it to phenylacetic acid.

In addition to its presence in mammals, phenethylamine is found in many other organisms and foods, such as chocolate, especially after microbial fermentation. In mammals, phenethylamine is produced from the amino acid L-phenylalanine by the enzyme aromatic L-amino acid decarboxylase via enzymatic decarboxylation. To a lesser extent, it also acts as a neurotransmitter in the human central nervous system. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace amine-associated receptor 1 (TAAR1) and inhibiting vesicular monoamine transporter 2 (VMAT2) in monoamine neurons. Phenethylamine ( PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans.

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