Management of Rash After Hunting in Woods
Start empiric doxycycline 100 mg twice daily immediately if you cannot exclude Rocky Mountain Spotted Fever (RMSF) or other tickborne rickettsial disease, as delay in treatment significantly increases mortality. 1
Immediate Assessment Priorities
Critical History Elements
Timing of rash relative to symptom onset: RMSF rash typically appears 2-4 days after fever begins, though up to 20% of patients never develop a rash 1. The absence of rash does not exclude tickborne disease 2.
Tick exposure history: Ask specifically about tick bites, though 40-60% of RMSF patients report no tick bite history 1. Common attachment sites include scalp, waist, armpits, groin, and under socks 2.
Associated symptoms: Fever, headache, myalgias, nausea, and vomiting are typical presenting symptoms in tickborne rickettsial diseases 3. The presence of high fever (>103°F) with rash warrants immediate concern 2.
Geographic and seasonal context: Peak tick activity occurs April through September, and tickborne diseases should be considered endemic throughout the contiguous United States 3.
Physical Examination Red Flags
Palm and sole involvement: This indicates advanced RMSF and is associated with severe illness requiring immediate treatment 1. This finding also suggests secondary syphilis, bacterial endocarditis, ehrlichiosis, or rat-bite fever 1.
Rash morphology and distribution: RMSF begins peripherally on ankles, wrists, or forearms as small (1-5 mm) blanching pink macules, progressing to maculopapular with central petechiae, then spreading centrally while sparing the face 1. Less than 50% have rash in the first 3 days 1.
Petechial or purpuric components: Rapidly progressive petechial or purpuric rash with high fever, severe headache, and altered mental status suggests meningococcemia, which has 20% risk of shock 1.
Immediate Laboratory Testing
Order these tests immediately but do not delay treatment while awaiting results:
Complete blood count with differential: Look for leukopenia, thrombocytopenia (platelet count <150 x 10⁹/L), or bandemia—thrombocytopenia is a critical red flag 1, 3.
Comprehensive metabolic panel: Identify hyponatremia and elevated hepatic transaminases (AST/ALT), both common in RMSF and ehrlichiosis 1, 3.
Note: Normal WBC count is frequently observed in RMSF and does not exclude the diagnosis 2. Serologic testing should not delay treatment, as antibodies may not be detectable early in illness 2.
Treatment Algorithm
Empiric Antibiotic Therapy
Initiate doxycycline 100 mg orally twice daily immediately if tickborne rickettsial disease cannot be excluded, regardless of patient age, including children under 8 years old 1, 4. For children, the dose is 2.2 mg/kg orally twice daily 2, 3, 4.
Expected response: Clinical improvement should occur within 24-48 hours 1. Continue treatment for a minimum of 5 days and until the patient has been afebrile for at least 3 days 2.
Rationale: The CDC reports RMSF mortality is 5-10%, with 50% of deaths occurring within 9 days of illness onset 1. Delay in treatment significantly increases mortality 1.
Additional Antimicrobial Coverage
Add ceftriaxone if meningococcemia cannot be excluded based on clinical presentation 1. Some experts recommend administering an intramuscular dose of ceftriaxone pending blood culture results, as meningococcal disease cannot be reliably distinguished from tickborne rickettsial disease on clinical grounds alone 2.
Medications to Avoid
Do not use the following antibiotics, as they are ineffective and may worsen outcomes:
Beta-lactams, macrolides, aminoglycosides, and sulfonamides are not effective against tickborne rickettsial diseases 2.
Fluoroquinolones have been associated with delayed fever resolution, increased disease severity, and longer hospital stays in rickettsial infections 2.
Sulfonamide antimicrobials (including trimethoprim-sulfamethoxazole) are associated with increased severity and death in RMSF 2.
Differential Diagnosis Considerations
Lyme Disease
If the rash has a central clearing or "bull's eye" appearance (erythema migrans), consider Lyme disease, particularly in endemic areas 2, 5. However, erythema migrans can appear as homogenous erythematous patches, interrupted annular patches, or patches with hemorrhagic or purpuric components 5.
Treatment: Doxycycline 100 mg twice daily for 7-21 days depending on manifestations 2.
Note: Doxycycline covers both Lyme disease and tickborne rickettsial diseases, making it the appropriate empiric choice 2.
Contact Dermatitis from Plants
Poison ivy, poison oak, and poison sumac cause intensely pruritic linear vesicular rashes that typically appear 12-48 hours after exposure. These rashes lack systemic symptoms like fever and do not require antibiotics.
Alpha-Gal Syndrome
A rash occurring 3-6 hours after eating mammalian meat (beef, pork, lamb) in someone with prior tick bites may represent alpha-gal syndrome 2. This is a delayed allergic reaction, not an acute infection, and does not present with fever.
Follow-Up and Prevention
Monitoring Response to Treatment
Clinical improvement expected within 24-48 hours of starting doxycycline 1.
Convalescent serology: Obtain serologic testing 2-4 weeks after illness onset to confirm diagnosis of RMSF, HGA, or HME 2.
Prevention Counseling
Provide specific tick bite prevention strategies:
Avoid tick habitats (wooded, brushy, or overgrown grassy areas) during peak activity (April-September) 2.
Wear light-colored clothing with long sleeves and tuck pants into socks or boots 2.
Apply DEET-containing insect repellent to exposed skin and permethrin to clothing 2.
Perform thorough tick checks after outdoor activities, focusing on scalp, waist, armpits, groin, and under socks 2.
Remove attached ticks immediately by grasping with fine-tipped tweezers close to the skin and pulling with steady pressure 2. Avoid folk remedies like petroleum jelly, fingernail polish, or lit matches 2.
Shower soon after activities in wooded areas 2.
Common Pitfalls to Avoid
Do not wait for laboratory confirmation before starting doxycycline if tickborne rickettsial disease is suspected 1.
Do not be reassured by absence of tick bite history—40-60% of RMSF patients report no tick bite 1.
Do not be reassured by absence of rash early in illness—less than 50% have rash in the first 3 days of RMSF 1.
Do not withhold doxycycline from children under 8 years old—the risk of death from untreated RMSF far outweighs the minimal risk of tooth staining from short courses 1, 3, 4.
Do not mistake drug eruption for rickettsial rash in patients treated with beta-lactams or sulfonamides—the rash may be a manifestation of rickettsial illness, not an allergic reaction 2.