Describing a scabies rash on physical exam means documenting a combination of primary lesions (papules, vesicles, nodules), their anatomical distribution, the presence or absence of pathognomonic burrows, and any secondary changes from scratching or infection. A thorough exam note captures each of these layers because scabies rarely presents as a single lesion type, and the pattern of findings is what clinches the diagnosis.
The Pathognomonic Burrow
The burrow is the single most diagnostic finding on exam. Describe it as a tiny, raised, serpentine (S-shaped or wavy) line that is grayish or skin-colored, typically a centimeter or more in length. Burrows represent the tunnel a female mite excavates through the uppermost layer of skin. They are most often found in the interdigital web spaces, the volar wrists, and the lateral aspects of the fingers. On exam, they can be subtle and easily mistaken for scratch marks, so note their linear, slightly irregular trajectory and the small papule or vesicle that often sits at one end, marking the mite’s current position.
If burrows are hard to visualize, the burrow ink test can help. Gently rub fountain pen ink over a suspicious site, then wipe off the excess with an alcohol swab. A burrow becomes visible as a wavy, ink-filled line where the tunnel has absorbed the ink. This is a quick bedside maneuver worth documenting in your exam note when used.
Primary Lesion Morphology
The most common primary lesions are erythematous papules, typically 1 to 3 mm, scattered across characteristic sites. Vesicles and vesicopustules also appear, particularly on the palms and soles in infants. In babies, pinkish-brown nodules are especially characteristic. For your exam description, note the lesion type, color, approximate size, and whether lesions are discrete or grouped.
A useful framework for the note: start with the dominant morphology (“scattered erythematous papules”), add secondary lesion types (“with intermixed vesicles”), then specify their distribution. Avoid vague terms like “rash” or “skin irritation.” Instead, name exactly what you see.
Nodular Scabies
Nodular scabies occurs in roughly 7 to 10% of cases and is more common in infants and young children. The nodules are erythematous, firm, and measure 5 to 20 mm. They cluster in the groin, on the genitalia, in the axillary folds, and over the buttocks. These nodules represent a delayed hypersensitivity reaction to mite proteins and can persist for months even after successful treatment, so their presence does not necessarily indicate active infestation.
On your exam note, describe them by size, color, firmness, and location. A typical entry might read: “Several firm, erythematous nodules measuring 8 to 12 mm in the bilateral axillary folds and inguinal creases.”
Distribution Pattern
Distribution is one of the strongest clues. In adults and older children, scabies favors the interdigital web spaces, flexor surfaces of the wrists, lateral edges of the hands, elbows, axillary folds, periumbilical area, belt line, buttocks, and genitalia. In men, papules or nodules on the penile shaft and glans are considered a hallmark finding. In women, lesions on the areolae are similarly characteristic.
In infants and young children, the distribution is broader and less predictable. Lesions can involve the palms, soles, scalp, face, and neck, areas typically spared in adults. Document which sites are involved and which are spared, because the pattern helps distinguish scabies from eczema, contact dermatitis, and other papular eruptions.
Secondary Changes From Scratching
Because scabies causes intense itch, particularly at night, you will almost always see secondary skin changes layered on top of the primary lesions. Excoriations and linear scratch marks are the most common. Crusting may develop over excoriated papules. In children especially, secondary impetigo is frequent, presenting as honey-colored crusts or superficial pustules overlying the primary scabies lesions.
Lichenification, or thickened and leathery skin, can develop in cases of prolonged scratching. When documenting these findings, distinguish them from the primary scabies lesions: “Multiple erythematous papules in the periumbilical region with overlying excoriations and scattered linear scratch marks” tells a clearer story than “excoriated rash on abdomen.”
Crusted Scabies
Crusted scabies, formerly called Norwegian scabies, looks dramatically different from classic scabies and warrants its own description. It presents with hyperkeratotic plaques that may be fissured, often with surrounding erythema. These thick, scaly plaques commonly involve the hands, feet, and interdigital web spaces but can be generalized. The plaques contain thousands to millions of mites, compared to the 10 to 15 mites in a typical infestation.
This presentation occurs almost exclusively in immunocompromised individuals. The itch is often less intense than in classic scabies, which can be misleading. On exam, note the plaque thickness, the degree of fissuring, and whether the distribution is localized or generalized. A description might read: “Thick, hyperkeratotic plaques with deep fissures over the dorsal hands and interdigital web spaces, with diffuse fine scaling on the forearms.”
Dermoscopy Findings
If you use a dermatoscope, several characteristic signs can confirm the diagnosis. The most frequently described is the “delta wing jet” or “triangle sign,” a small, dark, triangular structure at the leading end of a burrow that corresponds to the mite’s head and front legs. Trailing behind it, a wavy or curved line represents the burrow itself, sometimes called the “jet with contrail” sign. Ovoid structures along the burrow represent eggs or fecal pellets.
In crusted scabies, dermoscopy may reveal a “noodle pattern,” consisting of numerous closely packed, millipede-like burrow structures. Document which dermoscopic signs you identify, as visualization of the mite or its structures through dermoscopy meets the criteria for confirmed scabies under the 2020 International Alliance for the Control of Scabies diagnostic framework.
Structuring the Exam Note
A well-organized scabies exam note moves through four layers: primary lesion morphology, distribution, pathognomonic features, and secondary changes. Putting it together, a complete description might read:
- Primary lesions: Scattered erythematous papules, 1 to 3 mm, with intermixed vesicles
- Distribution: Bilateral interdigital web spaces, volar wrists, periumbilical area, and penile shaft
- Burrows: Several grayish, serpentine, thread-like lines measuring approximately 5 to 10 mm in the interdigital web spaces of the left hand
- Secondary changes: Linear excoriations and scattered crusted papules on the forearms and lower abdomen, consistent with chronic scratching
This structure gives any reader of the note, whether a consulting dermatologist, a covering provider, or a future clinician reviewing the chart, a clear mental picture of the exam findings and enough detail to support or reconsider the diagnosis.