Case Study: Bug Bite or Blister on a Trail Crew Project

The Setting

You are working as part of a backcountry trail crew in the Nantahala National Forest near the North Carolina-Tennessee border. The project involves brushing and tread work in steep, densely vegetated terrain with long approaches and limited access points. Summer conditions are hot and humid, and the crew has been in the field for several consecutive days with limited opportunities for full clothing changes or laundry.

The work requires long days of hiking with tools, frequent bushwhacking, and operating chainsaws while wearing heavy protective chaps. Everyone is sweaty, dusty, and a little grimy.

One afternoon during camp breakdown, one of your crew members, a 24-year-old female named Alex, mentions that the back of her right knee feels sore and itchy. She pulls up her pant leg to show you a small red bump on the inside-backside of the knee crease she describes as “very irritating.” It looks like a possible bug bite or friction irritation from the chainsaw chaps. You clean the area, apply basic wound care including some blister hotspot dressing to the area, and agree to keep an eye on it, circling the irritated area with a black permanent marker.

Over the next 36–48 hours, despite good hygiene and daily monitoring, the area becomes larger, more red, more painful, and increasingly warm to the touch. You begin to grow concerned that this may be developing into something more than a bug bite.

You are the crew’s designated Wilderness First Responder (WFR). You decide to complete a formal patient assessment.

SOAP Report

Subjective

The patient is a 24-year-old female whose chief complaint is increasing pain, redness, and swelling on the inside-backside of her right knee. Onset began approximately two days ago as a small itchy bump that resembled a bug bite. There is no known mechanism of injury. The patient reports the area has become progressively more painful and irritated despite daily cleaning and bandaging. She denies trauma to the area.

The patient is alert and oriented and able to ambulate, though knee flexion causes discomfort.

Objective

Patient Exam:
The patient is ambulatory with a mild limp. Inspection of the right posterior-medial knee reveals a circular area of redness approximately 2.75 inches (7 cm) in diameter with poorly defined borders. The center appears raised and firm with mild surrounding swelling. Skin is warm to the touch compared to surrounding tissue. No open drainage noted at this time. No red streaking visible proximally. No joint instability or decreased circulation noted. Distal CSM intact. No other wounds or injuries noted.

The area was outlined with a marker the previous evening; current redness extends approximately just less than an inch (2 cm) beyond the original marking.

Vital Signs

TIME	17:30
LOR	A+Ox4
HR	80, strong, regular
RR	18, regular, easy
SCTM	pink, warm, dry
B.P.	radial pulse present
Pupils	PERRL
T°	Not taken

History

Symptoms:	Localized pain, warmth, redness, swelling at right posterior knee. Increasing tenderness with movement and pressure. Mild fatigue. No chills, nausea, or vomiting reported.
Allergies:	Allergy to cats, no recent exposure, mild respiratory/ “hayfever-like” symptoms when exposed
Medications:	Denies any medications, prescription or over-the-counter.
Pertinent Hx:	Denies. No history of recurrent skin infections or reactions to insect bites/stings.
Last in/out:	The patient reports adequate hydration throughout the day, normal urine output, and regular bowel movement yesterday. Eating normally.
Events:	The patient has been wearing the same work pants and chainsaw chaps for multiple days with heavy sweating and friction at the knee crease. Exposures to mosquito bites and tick bites possible, but no specific bite or embedded ticks reported.

What is your Assessment and Plan?

Think about this before moving to the next page.

Assessment

• Suspected localized skin infection, possibly cellulitis or early abscess.
• Worsening despite appropriate field hygiene and wound care. 
• Low-grade fever suggests possible systemic involvement.
• Increased size and progression over 24–48 hours increases concern for bacterial infection.

Plan

• Cleaned area thoroughly with drinking water and mild soap.
• Applied clean dry dressing to reduce friction and contamination.
• Marked current border of redness for trend monitoring.
• Limited knee flexion and friction where possible.
• Encouraged hydration and rest.
• Continued close monitoring for:
  -Rapid expansion of redness
  -Development of drainage
  -Increasing pain
  -Fever or systemic symptoms
  -Red streaking
• Initiated evacuation plan due to continued progression despite appropriate care and increasing risk of deeper infection or mobility compromise.

Anticipated Problems

• Progression to abscess or systemic infection
• Increasing pain limiting ability to hike safely
• Delayed access to higher medical care
• Risk of spreading infection in field environment

What Happened?

The following morning, the redness had expanded well beyond the newly marked border, and the area was more painful and firm. Alex reported feeling more fatigued and slightly feverish overnight. Based on the continued progression and lack of response to conservative management, the crew initiated evacuation to the trailhead.

Alex was transported to an urgent care clinic later that afternoon. She was diagnosed with a staphylococcal skin infection and started on oral antibiotics. The provider confirmed that early evacuation was appropriate and likely prevented the infection from worsening or requiring more invasive treatment.

Comments

Alex made a full recovery and was able to return to work after completing the antibiotic course.

Skin infections in the backcountry often start subtly and can easily be mistaken for minor irritation, insect bites, or friction injuries. Warm, moist environments, dirty clothing, repeated friction, and limited hygiene all increase the risk of bacterial growth and infection. Monitoring trends over time—such as increasing redness, warmth, pain, size, and failure to improve with good wound care—is often more important than how the injury looks in a single moment.

Using simple tools like outlining redness with a marker, tracking vital signs, and documenting symptom progression can greatly improve decision-making and communication during evacuation. When a wound continues to worsen despite appropriate care, evacuation is the correct call. Having a reliable reference in the field can help reinforce decision thresholds and treatment principles when you’re tired, remote, or second-guessing yourself. Carrying resources like the NOLS Wilderness Medicine Field Guide allows you to double-check infection management, red flags, and evacuation criteria when it matters most. Even experienced providers benefit from having a trusted reference in their kit.