Continuing Education Activity

This activity explores the clinical implications of exposure to millipede toxins, a rarely encountered but potentially serious environmental hazard. Millipedes, arthropods of the class Diplopoda, defend themselves by secreting irritating chemicals from micropores along their sides. These secretions can cause a range of cutaneous and ocular symptoms, including allergic reactions, pigment changes, and, in severe cases, ocular damage. Due to the infrequency of such encounters and the overlap of symptoms with other conditions, millipede-related injuries may be underrecognized or misdiagnosed.

Participants develop the knowledge and skills needed to improve the identification, evaluation, and management of millipede toxin exposure. The activity highlights the importance of prompt decontamination, supportive care, and appropriate referrals—particularly to ophthalmology when the eyes are involved. Through a multidisciplinary approach, this activity aims to enhance clinical decision-making and interprofessional collaboration in managing this uncommon but clinically significant exposure.

Objectives:

• Identify key characteristics of millipedes and their defensive toxin secretion mechanisms.
• Differentiate millipede toxin exposure from other dermatologic and systemic conditions with similar presentations.
• Implement evidence-based decontamination and symptomatic treatment protocols for skin and mucous membrane exposure.
• Collaborate with dermatologists, ophthalmologists, emergency care providers, and other members of the interprofessional team for comprehensive management.

Introduction

Millipedes, one of the earliest known organisms on earth, belong to the class Diplopoda and comprise more than 13,000 species.[1][2] These organisms can live up to 7 years and typically inhabit areas covered in leaf litter and underground domains. Millipedes are primarily nocturnal, showing greater activity during the night. Millipedes range from 2 to 160 mm in size and may appear either flattened or cylindrical. Most species are brown or black, but some may display orange or red coloration. Millipedes are detritivores, meaning they primarily feed on decaying plant matter, which may contain fungi and feces. These organisms can be found on all continents except Antarctica; however, they prefer warm, humid climates such as the tropics.

Millipedes are commonly mistaken for centipedes; however, they have 2 pairs of legs per body segment, whereas centipedes have 1 pair per segment. Compared to centipedes, millipedes are much slower and try to avoid contact, whereas centipedes are quick and aggressive. Centipedes inject venom via front forcipules, sharp, thin appendages that pierce the skin.[3] In response to a threat, millipedes burrow and coil. Instead of injecting toxins, they secrete irritating compounds produced by specialized glands called ozadenes. These glands open to the environment through micropores called ozopores located along their sides. These secretions can cause burning, itching, blistering, and hyperpigmentation. Some compounds, such as hydrogen cyanide, also produce a distinct odor. The chemicals in these secretions can be particularly harmful to the eyes.[2][4] Pigmented lesions caused by millipede toxin exposure can mimic a wide range of focal and systemic conditions, making a detailed history and a thorough physical examination essential when assessing wounds related to millipede contact.[2][5] Occasionally, humans have allergic reactions to the toxins, requiring antihistamines or, rarely, epinephrine.[5][6]

Etiology

Millipedes lack fangs or stingers; therefore, they do not bite or sting. This arthropod is defensive and primarily seeks to deter predators. The standard defense mechanism includes coiling up to allow their chitinous exoskeleton to afford maximum protection. When threatened, the millipede secretes toxins from ozopores along their body. In humans, the primary mode of exposure is through inadvertent contact while dressing or working in beds of leaves. The toxins can have local effects on the skin or be unknowingly dispersed through mucous membranes or into the eyes.[5] Millipedes have a muscle unit affiliated with their pores that facilitates the expulsion of secretions. Secretions have been identified as containing caustic and malodorous chemicals, including hydrogen cyanide, hydrochloric acid, hydroquinones, benzoquinones, alkaloids, and phenols.[7][8][9][10][11][12] Benzoquinones cause skin discoloration or localized erythema and can irritate ocular structures. Hydrogen cyanide and hydrochloric acid are well-known skin irritants even in small doses, and can cause burning and pain. Effects also include a pungent foul odor. Most exposures are limited to focal involvement and resolve over days to weeks. Rarely, the millipede can spray their secretions over a wider area. Should the encounter involve a large family of millipedes, systemic effects such as nausea and vomiting may occur.[13]

Epidemiology

Epidemiological data are limited and derived primarily from case reports. Contact is more prevalent in tropical, humid areas. There are more instances of human contact during rainy seasons when millipedes may seek indoor shelter. Children and outdoor workers are more commonly affected. Exposure mainly occurs on the foot, followed by the hands, arms, face, and eyes. Accidental ingestion is largely limited to children. Harmful effects are more likely in tropical regions, where secretions may be more potent.[14]

Pathophysiology

The exact pathophysiology has not been thoroughly studied, and the literature is limited to case reports. Although several caustic compounds secreted by millipedes are known, the dose and duration of exposure can vary and are of uncertain clinical significance, except for those involving the eye. The chemical components of millipede secretions that impact skin and mucous membranes include hydrogen cyanide, hydrochloric acid, phenols, terpenoids, alkaloids, and benzoquinones. Benzoquinones, metabolites of benzene, are potent oxidizing agents used in various industrial and pharmaceutical applications and are responsible for the skin pigmentation observed after contact with millipede secretions.[15] Toluquinone is another potent oxidizing agent that causes skin necrosis through alkylation of proteins and can form reactive oxygen species, activating pathways that promote cell death.[16]

Most cases of skin irritation and hyperpigmentation resolve within several days to 1 month.[17] Species more prevalent in tropical areas emit a wider variety of chemicals in response to the greater biodiversity of predators. For example, tropical species harbor greater amounts of cyanide-based toxins. The increased number of compounds produced by more tropical millipedes causes heightened erythema, edema, blisters, pruritus, and pain, often referred to as a millipede burn.[18][19][20][21] Chemical impact on the eye includes keratoconjunctivitis, lacrimation, chemosis, corneal blistering, and, rarely, blindness. Reports of anaphylaxis are rare.[2][5][22][23]

History and Physical

Most exposures occur inadvertently within the home, especially during dressing, when millipedes crawl into shoes and similar spaces and are consequently crushed. Children are most frequently exposed to millipede toxins, often due to curiosity. Exposure to millipede toxins may also occur while digging or working in areas covered in leafy compost.[5] The history, as narrated by the patient or parent, may name either a centipede or millipede, as these arthropods are frequently confused for one another. If possible, the history should include the timing of symptom onset and progression, duration, travel history, environmental exposure, occupational risk factors, and dermatological disorders.[17] 

Physical findings include localized areas of inflammation, marked by edema and erythema. Hyperpigmentation may be present. The patient may report sensitivity, acute pain, or a mild burning sensation. The secreted chemicals may also cause bullae, vesicles, and ulceration. Skin discoloration can persist for up to several weeks.[18] If ocular exposure occurred, lacrimation and conjunctivitis may occur.[15]

Evaluation

Obtaining a detailed history and performing a thorough physical examination are essential.[24] No additional laboratory or radiographic testing is typically required, unless, for example, the vascular examination is equivocal in the context of an uncertain medical and recent history. Effects of contact with millipede secretions may mimic other pathologies, such as arterial insufficiency or diabetic skin necrosis. There is a case report of a patient who, after stepping on a millipede, presented with features worrisome for acral melanoma.[25]

Treatment / Management

Treatment is primarily supportive and begins with thorough cleansing of the affected area using soap and water to remove residual toxins and contaminants. Some clinicians recommend wiping the area with alcohol first or irrigating with an ether solvent, when available, to dissolve any toxins. Topical corticosteroids and analgesics such as lidocaine or benzocaine help alleviate symptoms that may be more severe in the setting of skin breakdown. In appropriate cases, a 1% hydrocortisone cream can be applied to affected areas 3 times daily. Ice may be used for comfort. Antihistamines and corticosteroids can be administered systemically for more significant reactions.[2][15] Ocular involvement requires irrigation with saline or water, an eye examination, and a follow-up appointment with an ophthalmologist. Urgent consultation may be warranted for patients with changes in visual acuity.[26]

Differential Diagnosis

Skin changes from contact with millipede toxins are similar in gross appearance to those found in arterial insufficiency, acute thrombosis or embolus, cholesterol embolus, or diabetic ulcer. The findings, depending on anatomical location, can also raise suspicion for non-accidental trauma in children. Additional diagnoses included burns, industrial chemical exposures, and contact with other arthropods.[27]

Prognosis

Exposure to millipede toxins is typically focal and self-resolving, with a favorable prognosis. Skin discoloration resolves within weeks, and local irritation and mild burning can dissipate in hours to days. Ocular involvement may require more extensive care and result in longstanding or even permanent damage. Rare cases of blindness are reported, particularly in less-developed areas of the world.[28]

Complications

 The most prevalent complications arising from contact with millipede toxins involve ocular exposure, including corneal ulceration and even blindness. There are also rare reports of anaphylaxis.[5]

Consultations

An ophthalmologist is needed for ocular involvement.

Deterrence and Patient Education

Contact with millipedes is relatively uncommon, so education is largely focused on preventing recurrence. Persons, especially children, are advised to assess clothing, including socks and shoes, before dressing. Protective clothing is advisable if occupational exposure is possible, and handling millipedes should be avoided. Removing damp and decaying organic material may reduce the millipede population around the home. Pesticides are available in the event of an infestation.[29][30]

Pearls and Other Issues

Physical manifestations of millipede contact can be mistaken for a range of pathologies, including acute ischemic changes of peripheral vascular disease, septic emboli, diabetic and venous stasis skin changes, calciphylaxis, and other conditions. Obtaining a detailed history and performing a thorough physical examination are essential for accurate diagnosis. In the setting of a crush encounter, the form of the millipede may be evident on the affected limb.[5]

Millipedes that live in soil may pose a risk of tetanus, so tetanus status should be confirmed in individuals presenting after millipede contact. Topical antihistamines should not be used in conjunction with oral antihistamines, and some clinicians feel they should be avoided altogether. Antibiotics in any form are typically unnecessary. Discoloration caused by millipede exposure may mimic bruising encountered in non-accidental trauma.[2]

Enhancing Healthcare Team Outcomes

Exposure to millipede secretions is generally self-limiting, with symptoms such as erythema, edema, pain, and hyperpigmentation resolving over days to weeks. Most cases can be effectively managed by a primary care provider or dermatologist, who can provide supportive care, symptom relief, and monitoring for complications. Follow-up is typically straightforward, focusing on resolving skin changes and preventing secondary infection. However, ocular exposure requires prompt evaluation by an ophthalmologist due to the potential for corneal injury, ulceration, or, in rare cases, vision loss. In such instances, immediate irrigation and specialized eye care are essential to prevent long-term complications.

Review Questions

• Access free multiple choice questions on this topic.
• Click here for a simplified version.
• Comment on this article.

References

1.

Brewer MS, Sierwald P, Bond JE. Millipede taxonomy after 250 years: classification and taxonomic practices in a mega-diverse yet understudied arthropod group. PLoS One. 2012;7(5):e37240. [PMC free article: PMC3352885] [PubMed: 22615951]

2.

Diaz JH. Poisonous, Venomous, or Harmless? Wilderness Environ Med. 2023 Dec;34(4):599-605. [PubMed: 37344256]

3.

Haddad Junior V, Amorim PCH, Cruz CRD, Amaral ALS. Centipede envenomation (Chilopoda): Case report. Rev Soc Bras Med Trop. 2022;55:e0601. [PMC free article: PMC9176727] [PubMed: 35674561]

4.

Marek PE, Shear WA. Myriapods. Curr Biol. 2022 Dec 05;32(23):R1294-R1296. [PubMed: 36473435]

5.

Haddad Júnior V, Haddad AMV, Barreiros JP. Myriapods (Diplopoda and Chilopoda): medical aspects of envenomations. Rev Soc Bras Med Trop. 2025;58:e003002025. [PMC free article: PMC12169687] [PubMed: 40531675]

6.

Nweze JE, Schweichhart JS, Angel R. Viral communities in millipede guts: Insights into the diversity and potential role in modulating the microbiome. Environ Microbiol. 2024 Feb;26(2):e16586. [PubMed: 38356108]

7.

Blum MS, Woodring JP. Secretion of Benzaldehyde and Hydrogen Cyanide by the Millipede Pachydesmus crassicutis (Wood). Science. 1962 Oct 26;138(3539):512-3. [PubMed: 17753947]

8.

Kuwahara Y, Omura H, Tanabe T. 2-Nitroethenylbenzenes as natural products in millipede defense secretions. Naturwissenschaften. 2002 Jul;89(7):308-10. [PubMed: 12216861]

9.

Ilić B, Unković N, Ćirić A, Glamočlija J, Ljaljević Grbić M, Raspotnig G, Bodner M, Vukojević J, Makarov S. Phenol-based millipede defence: antimicrobial activity of secretions from the Balkan endemic millipede Apfelbeckia insculpta (L. Koch, 1867) (Diplopoda: Callipodida). Naturwissenschaften. 2019 Jun 17;106(7-8):37. [PubMed: 31209578]

10.

Makarov SE, Curcić BP, Tesević VV, Jadranin MB, Vujisić LV, Curcić SB, Mandić BM, Sekulić TL, Mitić BM. Defensive secretions in three species of polydesmids (Diplopoda, Polydesmida, Polydesmidae). J Chem Ecol. 2010 Sep;36(9):978-82. [PubMed: 20809146]

11.

Bodner M, Vagalinski B, Makarov SE, Antić DŽ, Vujisić LV, Leis HJ, Raspotnig G. "Quinone Millipedes" Reconsidered: Evidence for a Mosaic-Like Taxonomic Distribution of Phenol-Based Secretions across the Julidae. J Chem Ecol. 2016 Mar;42(3):249-58. [PMC free article: PMC4839036] [PubMed: 26971956]

12.

Banks P, Funkhouser EM, Macias AM, Lovett B, Meador S, Hatch A, Garraffo HM, Cartwright KC, Kasson MT, Marek PE, Jones TH, Mevers E. The Chemistry of the Defensive Secretions of Three Species of Millipedes in the Genus Brachycybe. J Chem Ecol. 2024 Oct;50(9-10):478-488. [PMC free article: PMC11493816] [PubMed: 38853234]

13.

Rajashekar Ts, Okade R. Irritant contact dermatitis to accidental exposure of cyanide. Indian J Dermatol. 2013 Mar;58(2):162. [PMC free article: PMC3657255] [PubMed: 23716845]

14.

Hendrickson RG. Millipede exposure. Clin Toxicol (Phila). 2005;43(3):211-2. [PubMed: 15902798]

15.

De Capitani EM, Vieira RJ, Bucaretchi F, Fernandes LC, Toledo AS, Camargo AC. Human accidents involving Rhinocricus spp., a common millipede genus observed in urban areas of Brazil. Clin Toxicol (Phila). 2011 Mar;49(3):187-90. [PubMed: 21495889]

16.

Hyman S, Bilić R, Jensen A, Saladin S, Tsybrii Y, Nosko O, Topping D, Boies A, Giorio C, Roursgaard M, Møller P. Oxidative stress generated DNA damage by 6PPD and other tyre additives in A549 human lung epithelial cells. Sci Rep. 2025 Oct 13;15(1):35615. [PMC free article: PMC12518624] [PubMed: 41083604]

17.

Haddad V, Cardoso JL, Lupi O, Tyring SK. Tropical dermatology: Venomous arthropods and human skin: Part II. Diplopoda, Chilopoda, and Arachnida. J Am Acad Dermatol. 2012 Sep;67(3):347.e1-9; quiz 355. [PubMed: 22890735]

18.

Radford AJ. Millipede burns in man. Trop Geogr Med. 1975 Sep;27(3):279-87. [PubMed: 1103388]

19.

Radford AJ. Giant millipede burns in Papua New Guinea. P N G Med J. 1976 Sep;18(3):138-41. [PubMed: 1065155]

20.

Shpall S, Frieden I. Mahogany discoloration of the skin due to the defensive secretion of a millipede. Pediatr Dermatol. 1991 Mar;8(1):25-7. [PubMed: 1862020]

21.

Mason GH, Thomson HD, Fergin P, Anderson R. Spot diagnosis. The burning millipede. Med J Aust. 1994 Jun 06;160(11):718, 726. [PubMed: 8202008]

22.

HANEVELD GT. Eye lesions caused by the exudate of tropical millipedes. I. Report on a case. Trop Geogr Med. 1958 Jun;10(2):165-7. [PubMed: 13581185]

23.

Hudson BJ, Parsons GA. Giant millipede 'burns' and the eye. Trans R Soc Trop Med Hyg. 1997 Mar-Apr;91(2):183-5. [PubMed: 9196764]

24.

Lima CA, Cardoso JL, Magela A, Oliveira FG, Talhari S, Haddad Junior V. Exogenous pigmentation in toes feigning ischemia of the extremities: a diagnostic challenge brought by arthropods of the Diplopoda Class ("millipedes"). An Bras Dermatol. 2010 May-Jun;85(3):391-2. [PubMed: 20676478]

25.

Fracaroli TS, Miranda LQ, Maceira JP, Barcaui CB. Photoletter to the editor: Exogenous pigmentation after Diplopoda exposure leading to a dermatoscopic parallel ridge pattern on the plantar region. J Dermatol Case Rep. 2015 Sep 30;9(3):85-6. [PMC free article: PMC4619166] [PubMed: 26512306]

26.

Makarov SE, Bodner M, Reineke D, Vujisić LV, Todosijević MM, Antić DŽ, Vagalinski B, Lučić LR, Mitić BM, Mitov P, Anđelković BD, Lucić SP, Vajs V, Tomić VT, Raspotnig G. Chemical Ecology of Cave-Dwelling Millipedes: Defensive Secretions of the Typhloiulini (Diplopoda, Julida, Julidae). J Chem Ecol. 2017 Apr;43(4):317-326. [PMC free article: PMC5399059] [PubMed: 28303527]

27.

Herness J, Snyder MJ, Newman RS. Arthropod Bites and Stings. Am Fam Physician. 2022 Aug;106(2):137-147. [PubMed: 35977137]

28.

Lacy FA, Elston DM. What's eating you? millipede burns. Cutis. 2019 Apr;103(4):195-196. [PubMed: 31116815]

29.

Hash JM, Millar JG, Heraty JM, Harwood JF, Brown BV. Millipede Defensive Compounds Are a Double-Edged Sword: Natural History of the Millipede-Parasitic Genus Myriophora Brown (Diptera: Phoridae). J Chem Ecol. 2017 Feb;43(2):198-206. [PubMed: 28078624]

30.

Kalczynski JM, Piechnik M, Laterza C, Cuthbert D. Not Just Peds, Millipedes: An Arthropod Burn Case Report. Wilderness Environ Med. 2025 Mar;36(1):130-132. [PubMed: 39716912]

Disclosure: Trevor Lofgran declares no relevant financial relationships with ineligible companies.

Disclosure: Mia Marietta declares no relevant financial relationships with ineligible companies.

Disclosure: Steven Warrington declares no relevant financial relationships with ineligible companies.