This comes up constantly. Someone mentions they keep millipedes and the immediate response is "aren't they poisonous?" The short answer is: they're not venomous, some species do produce toxic secretions, and in practical terms they're safe to keep and handle. But the full answer involves a bit of chemistry and an important distinction that's worth getting right.
Venomous vs poisonous vs "produces defensive secretions"
Venom is injected, typically through a bite or sting. Centipedes are venomous. They have modified front legs called forcipules that inject venom into prey and predators. Millipedes don't have anything like this. They can't bite in any meaningful way and they have no sting.
Poison, strictly speaking, is something that harms you when you ingest or absorb it. Some millipede secretions could technically qualify, since they can be absorbed through skin or mucous membranes. But calling millipedes "poisonous" in the common sense of the word is misleading, because it implies a level of danger that doesn't match reality.
What millipedes actually do is produce chemical secretions from pores called ozopores, which run along the sides of their body. When threatened, they release these chemicals as a defensive measure. The composition varies by species, and that variation matters quite a bit.
What's in the secretions
The chemistry depends on the millipede's taxonomic group. The two main categories you'll encounter in the hobby are:
Benzoquinones: Produced by many species in the order Spirostreptida, which includes Archispirostreptus gigas (giant African millipede) and other commonly kept tropical species. Benzoquinones are irritant compounds. They can stain your skin a yellowish-brown colour that takes a day or two to fade. If they get into your eyes, they sting. On mucous membranes (nose, mouth), they cause irritation. On intact skin, the effect is usually mild staining and a slight smell.
Hydrogen cyanide (HCN): Produced by many species in the order Polydesmida, the flat-backed millipedes. Yes, this is actual cyanide. In the quantities produced by a single millipede, it's not going to poison you. But it's a genuine toxin, not just an irritant. You can often smell it as a faint bitter-almond odour. In an enclosed space with poor ventilation and many millipedes, the concentration could theoretically become problematic, though practical cases of this are essentially unheard of in the hobby.
Some species produce other compounds, including phenols, quinones, and various alkaloids. The chemical arsenal varies across the class Diplopoda, but benzoquinones and HCN are the two you'll mostly read about.
What this means for handling
For the vast majority of commonly kept species, handling is perfectly safe with basic precautions:
- Wash your hands after handling. Every time. This removes any secretion residue before you touch your face, rub your eyes, or eat something.
- If a millipede secretes on your hands (you'll often notice a slight colour change or smell), wash promptly with soap and water. The staining is cosmetic and fades within a day or two.
- Avoid touching your eyes, nose, or mouth while handling. Benzoquinones in the eyes are painful. Not dangerous in the long run, but genuinely unpleasant. Rinse with water if it happens.
- If you keep polydesmid species that produce HCN, handle in a well-ventilated room and wash hands thoroughly after.
People with sensitive skin may occasionally react to benzoquinone secretions with mild irritation or a slight rash. If this happens, it's not an allergy to the millipede itself but a reaction to the chemical. Less handling, or handling with gloves, solves it.
Are they dangerous to children or other pets?
Not in any practical sense, assuming normal supervision. A child who handles a millipede and then rubs their eyes will have a bad time for ten minutes, but it's not a medical emergency. A dog or cat that mouths a millipede might drool or spit because of the unpleasant taste, which is the whole point of the secretions from the millipede's perspective.
The risk is proportionate. You should supervise children handling millipedes and make sure they wash their hands after, just as you would with any animal. You probably shouldn't let your cat fish millipedes out of the enclosure, but that's more about the millipede's welfare than the cat's.
The curling defence
Chemical secretions are actually the second line of defence for most millipedes. The first response to a threat is to curl into a tight coil, tucking the legs and vulnerable underside inward and presenting the hard, calcified dorsal plates outward. Many species will do this before releasing any secretions. If your millipede curls up when you pick it up, it's not necessarily secreting. It's just startled. Set it down gently and give it a moment.
So are they safe to keep?
Yes. Millipedes are among the safest exotic invertebrates you can keep. They don't bite, they don't sting, and their chemical defences are mild enough that basic hand-washing after handling eliminates any real concern. The defensive secretions exist to deter predators in the wild, and a predator that gets a mouthful of benzoquinones will think twice about trying again. For a human who washes their hands, it's a non-issue.
The confusion partly comes from people mixing up millipedes and centipedes, which is unfortunate. Centipedes can deliver a genuinely painful, venomous bite. Millipedes cannot. If someone tells you millipedes are dangerous, they're almost certainly thinking of centipedes.