Why is squid ink safe to eat, while skunk spray is not? What makes the two liquids different from each other?
10.06.2025 07:40
Skunk spray is a mixture of thiols (mercaptans), which are small organic molecules with a sulhydryl group (–SH). Here is one of the simplest, methyl mercaptan.
The skunk's anal gland secretions contain seven major volatile components: three major thiols, three major thioacetates, and a methylquinoline. These are divided into thiols and acetate derivatives of the thiols. Two of these thiols, (E)-2-butene-1-thiol and 3-methyl-1-butanethiol, are responsible for the repellent odor. These two thiols constitute 51% to 70% of the anal gland secretions.
They smell terrible and they’re very flammable, like methane gas. Many thiols are part of normal human physiology, but some of them are toxic.
ISS Research & Development Conference Cancellation - NASA Watch
That article goes on to describe the toxic effects of skunk thiols, mainly on dogs and cats.
The major thiol of skunk spray is (E)-2-butene-1-thiol, shown below. At high concentrations, it is toxic to humans, and has even been used as a biological weapon (if extracted from skunks) or chemical weapon (if laboratory synthesized).
Squid ink is composed mainly of melanin and mucus, but with smaller amounts of dopamine, L-DOPA, and a few amino acids—nothing toxic. These are also natural parts of the human tissues.
Squid ink is meant only to conceal the animal so it can escape; it doesn’t need to be toxic to do that. Skunk thiols are meant to smell repugnant and irritate the eyes and mucous membranes, deterring enemies from approaching them.