Browse categories and answer follow-up questions to refine your symptom profile.
History
Presenting concern
Presentation overview
Tick bite
Concern for tick borne illness
Local symptoms
Systemic symptoms
Exposure details
Tick exposure characterization
Date and time of tick discovery
Estimated attachment duration
Tick appearance
Flat
Engorged
Tick removal method
Tick retained for identification
Geographic location of exposure
Endemic area for Ixodes
Travel outside region
Outdoor activities
Hiking
Camping
Yard work
Animal exposure
Dogs
Deer
Symptoms OPQRST
Symptom characterization
Onset
First symptom time and date
Relation to tick removal
Provocation and palliation
Worse with heat
Worse with friction
Relief with antihistamine
Relief with analgesic
Quality
Pruritic
Painful
Burning
Pressure
Region and radiation
Bite site location
Rash distribution
Migratory pain
Severity
Maximum temperature
Pain score
Timing
Progression pattern
Waxing and waning
Daily fevers
Associated symptoms
Associated symptom screen
Fever
Chills
Headache
Neck stiffness
Photophobia
Myalgia
Arthralgia
Arthritis
Fatigue
Nausea
Vomiting
Abdominal pain
Diarrhea
Rash
Neurologic symptoms
Facial weakness
Paresthesia
Weakness
Ataxia
Cardiac symptoms
Palpitations
Chest pain
Dyspnea
Presyncope
Syncope
Prior episodes and baseline
Baseline and prior history
Prior Lyme disease diagnosis
Prior tick borne illness
Prior erythema migrans
Baseline joint disease
Baseline neurologic disease
Alarm Features
Immediate escalation triggers
Resuscitation triggers
Hypotension
Altered mental status
Respiratory distress
Seizure
Anaphylaxis
Rapidly progressive rash
Purpura
Petechiae
Vital sign danger thresholds
High risk vitals
Temperature 39.5 C or higher with toxicity
Systolic blood pressure under 90 mmHg
Heart rate 130 or higher
Respiratory rate 30 or higher
Oxygen saturation under 92 percent on room air
High risk syndromes
Cannot miss presentations
Suspected Rocky Mountain spotted fever
Suspected meningitis or encephalitis
Suspected myocarditis
High degree atrioventricular block
Progressive ascending weakness
Tick paralysis concern
Severe hemolysis concern
Babesiosis risk with anemia or jaundice
Pregnancy and immunocompromise
Special population red flags
Pregnancy with fever or rash
Asplenia with febrile illness
Immunosuppression with systemic symptoms
Medications
Current and recent medications
Medication reconciliation
Antibiotics in last 30 days
Antipyretics
NSAIDs
Acetaminophen
Immunosuppressants
Corticosteroids
Biologics
Anticoagulants
Allergies and contraindications
Antibiotic safety screen
Tetracycline allergy
Prior severe cutaneous adverse reaction
Pregnancy or lactation considerations for doxycycline
High risk interactions
Doxycycline interaction screen
Warfarin interaction risk
Retinoids
Antacids and iron reducing absorption
Diet
Intake and hydration
Recent intake pattern
Poor oral intake
Vomiting limiting intake
Diarrhea limiting intake
Dehydration risk
Exposures relevant to symptoms
Exposure pattern
Alcohol intake
Caffeine intake
Recent raw milk
Recent undercooked meat
Review of Systems
Constitutional and infectious
Constitutional review
Fever
Chills
Night sweats
Weight loss
Skin and mucous membranes
Skin review
Expanding rash
Pruritus
Petechiae
Eschar
Neurologic
Neurologic review
Headache
Neck stiffness
Photophobia
Facial palsy
Radicular pain
Weakness
Paresthesia
Gait change
Cardiorespiratory
Cardiorespiratory review
Chest pain
Palpitations
Dyspnea
Syncope
Musculoskeletal
Musculoskeletal review
Arthralgia
Monoarthritis
Migratory joint pain
Gastrointestinal
Gastrointestinal review
Nausea
Vomiting
Abdominal pain
Diarrhea
Collateral History and Family History
Collateral sources
Additional history sources
Family witness of tick removal
Photo of tick
Photo of rash
Family history
Family risk factors
Immunodeficiency
Hemolytic anemia
Asplenia history
Household and community exposures
Shared exposures
Household members with tick bites
Pets with ticks
Local tick reports
Risk Factors
Exposure and geography
Epidemiologic risk
Ixodes habitat exposure
Endemic region for Lyme disease
Peak season exposure
Host risk factors for severe disease
Severe disease risk factors
Age 65 or older
Asplenia
Immunosuppression
Chronic liver disease
Pregnancy
Specific disease risk anchors
Disease specific risk factors
Babesiosis risk
Asplenia
Immunosuppression
Anaplasmosis risk
Ixodes exposure
Leukopenia or thrombocytopenia presentation
RMSF risk
Febrile illness with rash
Delayed doxycycline risk
Differential Diagnosis
Life threatening
Life threatening causes
Rocky Mountain spotted fever
Fever with headache
Rash
Thrombocytopenia
Hyponatremia
Ehrlichiosis
Fever
Leukopenia
Thrombocytopenia
Elevated transaminases
Anaplasmosis
Fever
Cytopenias
Elevated transaminases
Babesiosis
Hemolytic anemia
Jaundice
Dark urine
Meningitis or encephalitis
Neck stiffness
Altered mental status
Lyme carditis
Syncope
Palpitations
Atrioventricular block
Sepsis of alternate source
Pneumonia
Urinary infection
Common
Common causes
Early localized Lyme disease erythema migrans (A69.2)
Expanding annular rash
May be non pruritic
Local hypersensitivity reaction to bite
Small localized erythema
Improves within 48 hours
Viral syndrome
Upper respiratory symptoms
Diffuse myalgias
Cellulitis
Warmth
Tenderness
Purulence
Less common
Less common causes
Tick paralysis
Ascending weakness
Areflexia
Tularemia (A21.9)
Ulceroglandular lesion
Lymphadenopathy
Powassan virus encephalitis
Rapid neurologic decline
Meningoencephalitis features
STARI
EM like rash in non Lyme region
Lone star tick exposure
Mimics and pitfalls
Mimics
Drug eruption
New medication exposure
Diffuse morbilliform rash
Meningismus from dehydration
Orthostasis
Dry mucous membranes
Acute rheumatic conditions
Crystal arthritis
Septic arthritis
Past Medical History
Comorbidities
Relevant chronic conditions
Asplenia
Immunosuppression
HIV
Chronic kidney disease
Chronic liver disease
Cardiac conduction disease
Surgical and device history
Procedures and devices
Pacemaker
Prosthetic joints
Valve replacement
Baseline function
Baseline status
Baseline mobility
Baseline neurologic deficits
Physical Exam
Vitals and general
Initial assessment
Temperature trend
Hemodynamic stability
Toxic appearance
Skin exam
Skin and bite site
Tick parts retained
Local reaction size
Expanding rash size progression
Erythema migrans morphology
Central clearing
Multiple lesions
Petechiae
Purpura
Eschar
Head and neck
Head and neck
Conjunctival injection
Meningeal signs
Lymphadenopathy
Cardiopulmonary
Cardiac and lung exam
Bradycardia
New murmur
Signs of heart failure
Pulmonary crackles
Neurologic
Neurologic exam
Mental status
Cranial nerves
Facial symmetry
Motor strength
Reflexes
Gait
Sensory exam
Musculoskeletal
Joint exam
Monoarthritis
Effusion
Range of motion limitation
Migratory tenderness
Lab Studies
Core ED labs when systemic illness
Baseline laboratory evaluation
CBC with differential
CMP
AST
ALT
Bilirubin
Creatinine
Sodium
CRP
Tick borne targeted testing
Disease specific testing
Lyme serology
Two tier testing when compatible syndrome
Early localized erythema migrans diagnosis is clinical
Early serology may be negative
Anaplasma testing
PCR early illness
Peripheral smear morulae low sensitivity
Ehrlichia testing
PCR early illness
Serology paired samples when needed
Babesia testing
Peripheral smear
PCR if smear negative with high suspicion
Sepsis and complications
Severity evaluation
Blood cultures if febrile and toxic
Lactate if sepsis concern
Coagulation studies if purpura
Hemolysis labs if anemia
LDH
Haptoglobin
Reticulocyte count
Test pitfalls and timing
Interpretation pearls
Asymptomatic serologic testing after tick bite is not useful
Empiric doxycycline should not be delayed for suspected rickettsial disease
Tick testing for infection is not recommended for clinical decision making
Imaging
Scoring Systems
Decision tools and criteria
High risk Ixodes bite criteria for Lyme prophylaxis
Ixodes species likely
Endemic region exposure
Attachment 36 hours or longer
Prophylaxis within 72 hours of removal
Doxycycline safe for patient
SILC score for high degree atrioventricular block
Low probability 0 to 2
Intermediate probability 3 to 6
High probability 7 to 12
MRI
MRI indications
Suspected encephalitis with focal deficits
Suspected myelitis or radiculopathy
Consider lumbar spine MRI for severe radicular pain with neuro deficits
CT
CT indications
CT head if altered mental status with concern for intracranial process
CT chest if alternate source and respiratory distress
Contrast risk screening
Kidney injury
Prior contrast reaction
Ultrasound
Ultrasound use cases
Joint effusion assessment
Soft tissue abscess evaluation at bite site
Cardiac POCUS if shock or myocarditis concern
Special Tests
Tick and rash evaluation
Bedside and practical tests
Tick identification support
Photo documentation
Local public health tick ID options
Erythema migrans clinical diagnosis
Expanding rash over days
Size typically greater than 5 cm
Neurologic and CSF evaluation
Lumbar puncture considerations
Suspected meningitis or encephalitis
Opening pressure when indicated
CSF studies
Cell count and differential
Protein
Glucose
CSF PCR per syndrome and local protocol dependent
Joint and hematology procedures
Procedural diagnostics
Arthrocentesis for hot swollen joint
Cell count
Crystal analysis
Gram stain and culture
Peripheral smear for babesiosis
Parasitemia estimate
Repeat smear if high suspicion
ECG
Indications and key findings
ECG use in tick borne illness
Cardiac symptoms
Palpitations
Chest pain
Dyspnea
Syncope
Bradycardia
Known or suspected Lyme disease with systemic symptoms
Lyme carditis patterns
Conduction abnormalities
PR prolongation
First degree atrioventricular block
Second degree atrioventricular block
Third degree atrioventricular block
ECG escalation thresholds
High risk ECG thresholds
PR interval 300 ms or longer
Second degree atrioventricular block
Third degree atrioventricular block
Ventricular escape rhythm
Serial ECG logic
Monitoring strategy
Repeat ECG with symptom change
Continuous monitoring when high grade block or PR 300 ms or longer
Assessment
Problem representation
Clinical synthesis
Tick exposure with symptoms compatible with tick borne illness
Time since exposure
Region risk level
Working diagnoses
Working diagnosis set
Tick bite with no symptoms
Lyme prophylaxis eligibility determination
Observation pathway if not eligible
Early localized Lyme disease erythema migrans (A69.2)
Clinical diagnosis when typical
Serology may be negative early
Suspected rickettsial disease
RMSF concern if fever with headache and rash
Empiric doxycycline threshold low
Suspected anaplasmosis or ehrlichiosis
Cytopenias
Elevated transaminases
Suspected babesiosis
Hemolysis features
Asplenia risk
Severity and risk stratification
Risk stratification
Toxic appearance or organ dysfunction
Neurologic involvement
Cardiac involvement
Hemolysis severity
Pregnancy
Immunocompromise
Plan
First 5 minutes for the critical patient
Immediate stabilization
Cardiac monitoring when unstable or conduction concern
Two large bore IV if sepsis concern
Oxygen for hypoxemia
Point of care glucose if altered mental status
Early antibiotics for suspected rickettsial disease
Diagnostic sequencing
Testing plan
CBC and CMP when systemic symptoms
ECG when cardiac symptoms or bradycardia
Targeted tick borne testing based on syndrome
Lumbar puncture when meningitis or encephalitis concern
Empiric and directed therapy
Antibiotic strategy
Lyme post exposure prophylaxis when high risk bite
Doxycycline 200 mg orally once
Children doxycycline 4.4 mg per kg orally once
Maximum 200 mg once
Within 72 hours of tick removal
Not for low risk bites
Suspected RMSF
Doxycycline 100 mg orally or IV every 12 hours
Children doxycycline 2.2 mg per kg every 12 hours
Minimum 5 days
Continue at least 3 days after fever resolves
Early localized Lyme erythema migrans
Doxycycline 100 mg orally every 12 hours
Typical duration 10 days local protocol dependent
Alternative amoxicillin when doxycycline unsuitable
Lyme carditis severe
Hospitalization and IV ceftriaxone
Ceftriaxone 2 g IV daily
Switch to oral when improving per guideline
Babesiosis suspected or confirmed
ID consult recommended
Severe disease admission criteria low threshold
Symptom control and supportive care
Supportive management
Antipyretics
IV fluids for dehydration
Antiemetics if vomiting
Reassessment loop
Reassessment triggers
Repeat vitals within 60 minutes if febrile or tachycardic
Repeat neuro exam if headache or weakness
Repeat ECG if palpitations or presyncope
Escalate level of care for worsening rash or hypotension
Consultation plan
Specialty involvement
Infectious diseases for severe or atypical presentations
Cardiology for high grade atrioventricular block or PR 300 ms or longer
Neurology for encephalitis or progressive weakness
Public health notification local protocol dependent
Disposition
Admission and ICU criteria
Higher level of care indications
Shock or persistent hypotension after fluids
Altered mental status
Meningitis or encephalitis concern
PR interval 300 ms or longer
Second or third degree atrioventricular block
Significant anemia or hemolysis
Parasitemia concern in babesiosis
Inability to tolerate oral therapy
Observation pathway
Observation suitable scenarios
Moderate systemic symptoms without organ dysfunction
Pending key labs with stable vitals
Mild conduction abnormalities with reliable follow up
Discharge criteria
Discharge requirements
Hemodynamic stability
No alarm features
Able to tolerate oral intake
Reliable follow up within 24 to 72 hours when indicated
Clear return precautions
Follow up timing
Follow up plan
Primary care within 1 week
Infectious diseases within 1 to 2 weeks if confirmed Lyme complications
Cardiology within 24 to 72 hours for mild Lyme carditis local protocol dependent
Discharge Instructions
Copy discharge instructions
Patient instructions
You were seen after a tick bite or possible tick borne illness
Watch for symptoms for 30 days after a tick bite
Fever
New rash that expands over days
Severe headache
Neck stiffness
New weakness or facial droop
Palpitations
Chest pain
Fainting
New joint swelling
Dark urine or yellow skin
Return to the emergency department right away if any of the above occur
If you were given antibiotics, take them exactly as prescribed
Avoid excess sun exposure while taking doxycycline
Seek care if vomiting prevents keeping medication down
Follow up with your clinician within the recommended time window
References
Guidelines and key sources
Reference list
Infectious Diseases Society of America IDSA AAN ACR Lyme disease guideline 2020
CDC Lyme disease post exposure prophylaxis handout
CDC Lyme treatment and post exposure antibiotics page 2024
Public Health Ontario Lyme disease antibiotic prophylaxis algorithm 2023
Canada Public Health Lyme disease prevention and transmission page 2024
CDC Rocky Mountain spotted fever clinical care page 2025
CDC Lyme carditis clinical care page 2024
Suspicious Index in Lyme Carditis score derivation Besant 2018
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.