Cutaneous anthrax is the most common form of anthrax, accounting for >95% of all anthrax infections, caused by Bacillus anthracis spore inoculation through skin breaks. [1-2] It is characterized by a painless, pruritic papule that evolves into a vesicle and then a classic black eschar with surrounding edema. [2-3] Without treatment, mortality can reach 10–20%; with appropriate antibiotics, death is rare. [1][4]
1. History
- Exposure history is paramount: contact with livestock (cattle, goats, sheep), animal hides, wool, bone meal, or contaminated animal products [2][5]
- Occupational exposure: farmers, veterinarians, abattoir workers, hide/wool processors, drum makers using animal skins [2]
- Bioterrorism context: mail handling, suspicious powder exposure, mass casualty event [4]
- Incubation period: 1–12 days (mean ~5 days) [3-4]
- Symptom progression: initial pruritus at inoculation site → painless papule → vesicle with clear/serosanguinous fluid → painless ulcer → black eschar over 24–48 hours [2-3]
- Characteristically painless — pain suggests secondary bacterial superinfection [2]
- Associated symptoms: mild fever, headache, malaise [3]
- Ask about recent travel to endemic regions (sub-Saharan Africa, Central/South Asia, Middle East) [5]
2. Alarm Features
- Extensive or "malignant" edema, especially of the head, neck, or thorax — risk of airway compromise [2-3]
- Signs of systemic involvement: high fever, chills, tachycardia, hypotension [6]
- Neurologic signs: headache with cranial nerve deficits, seizures, altered mental status (suggests meningitis) [6]
- Nausea/vomiting, abdominal pain (associated with later fatal outcomes) [6]
- Bacteremia at any point — significantly associated with mortality [6]
- Coagulopathy or DIC [6]
- Lymphadenopathy within the first 3 days of hospitalization — associated with fatal outcomes [6]
- Multiple lesions or rapidly expanding edema [7]
- Any suspicion of concurrent inhalational exposure (bioterrorism context) [4]
3. Medications
First-line treatment (naturally acquired, uncomplicated)
- Ciprofloxacin 500 mg PO BID or doxycycline 100 mg PO BID for 7–10 days [6-8]
- Penicillin V 500 mg PO QID for 7–10 days if isolate is penicillin-susceptible (IDSA strong recommendation) [3]
- Amoxicillin 500 mg PO TID is an alternative if susceptibility confirmed [9]
Severe cases (systemic involvement, extensive edema, head/neck lesions):
Bioterrorism-related
- Duration extended to 60 days (due to risk of concurrent inhalational exposure) [3][8]
- Consider anthrax vaccine adsorbed (AVA) in conjunction with PEP antibiotics [7]
Corticosteroids: May reduce edema duration, particularly in malignant edema, though evidence is limited [1][3]
Contraindicated: Do NOT incise, debride, or excise the eschar — this can worsen systemic spread [2]
4. Diet
- No specific dietary triggers or restrictions
- Ensure adequate hydration, especially if febrile or systemically ill
- Avoid consumption of undercooked meat from potentially infected animals in endemic areas (prevention of GI anthrax)
5. Review of Systems
- Constitutional: Fever, chills, malaise, fatigue, night sweats
- Skin: Pruritus, painless lesion, edema, vesicle formation, eschar
- Neurologic: Headache, confusion, neck stiffness, focal deficits (rule out meningitis)
- GI: Nausea, vomiting, abdominal pain (may indicate GI anthrax or systemic disease)
- Respiratory: Dyspnea, chest tightness (rule out inhalational anthrax, airway compromise from neck edema)
- Lymphatic: Regional lymphadenopathy, lymphangitis
6. Collateral History and Family History
- Collateral: Identify co-exposed individuals (household members, coworkers) — critical for public health response [5]
- Determine if others have similar lesions or respiratory illness
- Occupational contacts with animals or animal products
- Family history is not directly relevant (non-hereditary), but household exposure patterns matter
- Mandatory reporting: Any suspected case must be reported immediately to local/state health department and CDC [5][9]
7. Risk Factors
- Occupational exposure: Agricultural workers, veterinarians, wool/hide processors, laboratory workers [2]
- Contact with infected animals (cattle, sheep, goats) or their products [5][10]
- Handling imported animal hides, drums, or wool from endemic regions [6]
- Skin breaks, cuts, or abrasions at time of exposure [2][4]
- Endemic regions: sub-Saharan Africa, Central Asia, Middle East, parts of South America [5]
- Male predominance (~79% in case series) [1][10]
- Bioterrorism exposure (mail handling, suspicious packages) [4]
8. Differential Diagnosis
- Staphylococcal furuncle/carbuncle — typically painful and purulent (anthrax is painless and non-purulent) [9]
- Ecthyma/ecthyma gangrenosum — ecthyma gangrenosum usually in neutropenic patients with Pseudomonas bacteremia [9]
- Tularemia (ulceroglandular) — painful ulcer with lymphadenopathy; exposure to rabbits/ticks [4]
- Cutaneous leishmaniasis — painless, slowly evolving ulcer; travel to endemic areas; no black eschar [5]
- Brown recluse spider bite — painful with necrosis [9]
- Orf (ecthyma contagiosum) — contact with sheep/goats; no large eschar or gelatinous edema [9]
- Scrub typhus/rickettsial spotted fevers — eschar with fever; tick/mite exposure [4]
- Buruli ulcer (M. ulcerans) — painless, expanding ulcer; tropical freshwater exposure [5]
- Rat bite fever — eschar at bite site with systemic symptoms [4]
- Vasculitis — noninfectious eschar; systemic features [4]
Key distinguishing feature: The combination of a painless black eschar + surrounding non-purulent edema + exposure history is highly characteristic of cutaneous anthrax. [2-3]
9. Past Medical History
- Prior anthrax infection (increases risk of severe vaccine reactions; avoid AVA in these patients) [7]
- Immunocompromising conditions — may require extended PEP duration (60 days) [6]
- Prior anthrax vaccination status
- Allergies to fluoroquinolones, tetracyclines, or penicillins (affects antibiotic selection)
- Chronic skin conditions or wounds that may serve as entry points
10. Physical Exam
- Vital signs: Usually stable in uncomplicated cases; fever mild to moderate; hypotension is an alarm sign [6]
- Skin: Examine for the classic progression:
- Early: pruritic papule → vesicle with clear/serosanguinous fluid
- Late: painless, depressed black eschar with surrounding non-pitting edema and satellite vesicles [2-3]
- Edema often disproportionate to lesion size, especially on head/neck [2]
- Lesion is non-purulent — pus suggests secondary infection [2]
- Lymph nodes: Regional lymphadenopathy and lymphangitis [4]
- Airway: Assess for stridor, voice changes, or dyspnea if head/neck involvement (malignant edema) [3]
- Neurologic: Mental status, meningeal signs, cranial nerve exam [6]
- Common lesion locations: hands, forearms, face, neck [4][10]
11. Lab Studies
- Lesion culture: Unroof vesicle and soak 2 dry swabs in fluid; or rotate 2 moist swabs under eschar edge — positive >80% in untreated lesions [3]
- Gram stain of vesicular fluid: large gram-positive bacilli in chains ("boxcar" appearance) [4]
- Blood cultures: Almost always negative in uncomplicated cutaneous anthrax; positive blood cultures indicate systemic disease and are associated with mortality [3][6]
- CBC: WBC usually normal; mild leukocytosis possible [3]
- Coagulation studies: If systemic disease suspected (DIC screening) [6]
- Punch biopsy for immunohistochemical (IHC) staining and/or PCR if cultures negative or patient pretreated with antibiotics [3]
- Serologic testing (anti-PA IgG): useful for retrospective confirmation [3]
- Do NOT squeeze lesions to obtain culture material [3]
12. Imaging
- Not routinely needed for uncomplicated cutaneous anthrax
- Chest X-ray or CT chest if any concern for concurrent inhalational anthrax (widened mediastinum, pleural effusions, mediastinal lymphadenopathy) [2]
- CT head if meningeal signs present [2]
- Soft tissue imaging (CT or ultrasound) may be considered if extent of deep tissue edema is unclear or airway compromise is a concern
13. Special Tests
- PCR for B. anthracis — highly specific; can be performed on vesicular fluid, swabs, or biopsy tissue [3][10]
- Immunohistochemical (IHC) staining of biopsy specimens — useful when cultures are negative [3]
- Anthrax triage checklist (CDC): developed for mass exposure events to rapidly distinguish anthrax from non-anthrax illness (sensitivity ~95% for adult cases) [11]
- Gamma phage lysis testing and direct fluorescent antibody (DFA) testing — performed at reference laboratories (LRN)
- All specimens should be handled with BSL-2 precautions at minimum; notify laboratory before sending suspected anthrax specimens [9]
14. ECG
- Not routinely indicated for uncomplicated cutaneous anthrax
- Obtain ECG if systemic toxicity, hemodynamic instability, or signs of sepsis
- No pathognomonic ECG findings; monitor for tachycardia or signs of myocardial depression in severe/systemic cases
15. Assessment
Severity stratification
- Uncomplicated/localized: Painless eschar with minimal edema, no systemic symptoms — most common presentation; excellent prognosis with antibiotics [12]
- Complicated: Extensive edema ("malignant edema"), head/neck involvement, systemic symptoms (fever, lymphadenopathy), or signs of bacteremia — higher morbidity and mortality [2][6]
- Systemic/meningitis: Rare progression; carries very high mortality even with treatment [12]
Cutaneous anthrax can be self-limiting in 80–90% of cases, but antibiotic therapy is always recommended to prevent systemic dissemination and reduce mortality from ~20% to near zero. [2-3]
16. Treatment Plan
Initial stabilization
- ABCs; assess airway if head/neck edema present
- IV access if systemic symptoms
Antibiotic therapy (per CDC 2023 Guidelines and IDSA): [3][6]
Additional considerations
- Antibiotics do not accelerate eschar healing but prevent systemic spread [3-4]
- Corticosteroids significantly reduced edema duration in one retrospective study (P < 0.002) [1]
- Airway management (intubation/tracheostomy) may be required for severe head/neck malignant edema [3]
- Do not incise or debride the eschar [2]
- Switch antibiotics based on susceptibility testing when available [6]
17. Disposition
Admission criteria
- Extensive or malignant edema, especially head/neck [3][7]
- Signs of systemic involvement: high fever, hypotension, tachycardia, bacteremia [6]
- Neurologic symptoms suggesting meningitis [6]
- Inability to tolerate oral medications
- Bioterrorism-related cases with concern for concurrent inhalational exposure [4]
Discharge criteria
- Uncomplicated, localized cutaneous lesion with no systemic symptoms
- Able to tolerate oral antibiotics
- Reliable follow-up and understanding of return precautions
Specialist consultation triggers
- Infectious disease consultation for all confirmed/suspected cases
- Surgery/ENT if airway compromise from malignant edema
- Critical care if hemodynamic instability or meningitis
- Public health notification is mandatory — contact local/state health department and CDC immediately [5][9]
18. Follow Up / Return Precautions
- Follow-up: Within 24–48 hours for initial reassessment; then every 2–3 days until eschar begins to separate (typically 12–14 days) [3]
- Eschar will dry, loosen, and slough over 1–2 weeks — this is expected and does not require intervention [4]
- Complete full antibiotic course even if lesion appears improved
Return immediately for
- Increasing edema, especially spreading to face/neck/chest
- New fever, chills, or worsening malaise
- Difficulty breathing or swallowing
- Headache with neck stiffness or confusion
- New skin lesions at distant sites
Patient counseling
- Cutaneous anthrax is not transmitted person-to-person [5]
- Avoid manipulating or picking at the eschar
- Wound care: keep clean and covered; no debridement
- Expected course: eschar separates in ~2 weeks; most lesions heal without scarring in 80–90% of cases [2]
- Contacts and co-exposed individuals should be evaluated and may need post-exposure prophylaxis [6]
References
1. Rational Corticosteroids Administration and Antibiotic Treatment Is Key to Managing Cutaneous Anthrax. — Xia L, Yan Z, Wei LS, et al. BMC Infectious Diseases. 2024.
2. Anthrax. — Dixon TC, Meselson M, Guillemin J, Hanna PC. The New England Journal of Medicine. 1999.
3. Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. — Stevens DL, Bisno AL, Chambers HF, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2014.
4. Anthrax as a Biological Weapon, 2002: Updated Recommendations for Management. — Inglesby TV, O'Toole T, Henderson DA, et al. The Journal of the American Medical Association. 2002.
5. Post-Travel Dermatologic Conditions. — Karolyn A. Wanat and Scott A. Norton CDC Yellow Book. 2025.
6. CDC Guidelines for the Prevention and Treatment of Anthrax, 2023. — William A. Bower MD, Yon Yu PharmD, Marissa K. Person MSPH, et al United States Centers for Disease Control and Prevention. 2025.
7. Conference Report on Public Health and Clinical Guidelines for Anthrax. — Stern EJ, Uhde KB, Shadomy SV, Messonnier N. Emerging Infectious Diseases. 2008.
8. Clinical Management of Potential Bioterrorism-Related Conditions. — Adalja AA, Toner E, Inglesby TV. The New England Journal of Medicine. 2015.
9. Recognition and Management of Anthrax — An Update. — Swartz MN. The New England Journal of Medicine. 2001.
10. Retrospective Evaluation of 13 Cases of Anthrax in Children: A Clinical and Therapeutic Perspective. — Erdeniz EH, Dönmez AS. Vector Borne and Zoonotic Diseases. 2026.
11. Development and Performance of a Checklist for Initial Triage After an Anthrax Mass Exposure Event. — Hupert N, Person M, Hanfling D, et al. Annals of Internal Medicine. 2019.
12. Systematic Review of Hospital Treatment Outcomes for Naturally Acquired and Bioterrorism-Related Anthrax, 1880-2018. — Person MK, Cook R, Bradley JS, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2022.