Question explored with the scientific record
rash on scone following scabies - won’t go away - very itchy
The short version: a persistent, intensely itchy rash after scabies treatment is common and does not mean the treatment failed, but you need to rule out ongoing infestation.
The evidence shows that a single application of permethrin 5% cream cures about 98% of patients, with cure rates at two weeks of 88-96% across multiple studies [1, 4, 5, 8]. Two doses of oral ivermectin (200 µg/kg, taken a week apart) reach similar cure rates of 95-100% [4, 7, 8]. The itch itself comes from the immune response to the mites, their eggs, and their waste, not from the live mites alone. That immune reaction can persist for weeks after the mites are dead. The skin's barrier is disrupted, and the inflammatory cascade (IL-1a, GM-CSF, and other cytokines are upregulated by the infestation itself [14]) takes time to settle.
The real question is whether the mites are still alive. If the rash is new burrows, or if it spread to a new person in the household after treatment, that points to treatment failure or reinfestation. If the rash is just the old spots still itching, that is post-scabetic pruritus and will fade over weeks. The evidence does not include a long-term safety study of repeated permethrin applications, but the cure rate from a single course is high enough that a second course is reasonable if symptoms persist beyond four weeks. The studies here were not funded by manufacturers in a way that would bias the cure-rate numbers, but none of them compared treated to untreated groups over a long follow-up, so the natural resolution rate is unknown.
| Treatment | Cure rate at 2 weeks | Notes |
|---|---|---|
| Permethrin 5% cream, single application | 88-98% | Most effective single-dose option [1, 4, 5, 8] |
| Oral ivermectin, two doses (200 µg/kg, 1 week apart) | 95-100% | Equivalent to permethrin after second dose [4, 7, 8] |
| Benzyl benzoate | 80-92% | Less effective than permethrin [5, 8] |
| Lindane | 84% | Banned in many places; neurotoxic [1, 17] |
My call: if you have no new burrows and no spread to others, wait four weeks from the last treatment. If the itch is still severe or new spots appear, retreat with permethrin or two doses of ivermectin. Confidence: moderate — the cure rates are well established, but the evidence does not tell you how long post-scabetic itch normally lasts in an individual, and no study followed untreated controls to measure the background rate of spontaneous resolution.
Sources examined 18
-
PERMETHRIN VERSUS CROTAMITON AND LINDANE IN THE TREATMENT OF SCABIES
This study compares the efficacy of permethrin, crotamiton, and lindane in treating scabies, finding that permethrin is significantly more effective, particularly in infants and young children.
DOI: 10.1111/j.1365-4362.1992.tb03958.x -
Atypical Scabies Presenting as Annular Patches
This case report describes a 3-year-old girl with atypical scabies presenting as well-defined annular patches, which was successfully treated with permethrin cream after 2.5 years of ineffective treatments.
DOI: 10.1111/j.1525-1470.2012.01840.x -
Effectiveness of permethrin standard and modified methods in scabies treatment
This study evaluates the effectiveness of standard versus modified permethrin application methods for treating scabies in a high-prevalence boarding school setting, finding no significant difference in cure rates between the two approaches.
DOI: 10.13181/mji.v23i2.594 -
A comparative study of oral ivermectin and topical permethrin cream in the treatment of scabies☆, ☆☆
This study compares the efficacy of oral ivermectin and topical permethrin cream in treating scabies, finding that while permethrin is superior in single-dose application, two doses of ivermectin are equally effective.
DOI: 10.1016/s0190-9622(00)90131-2 -
Efficacy, acceptability and cost effectiveness of four therapeutic agents for treatment of scabies
This study evaluates the efficacy, acceptability, and cost-effectiveness of four therapeutic agents—ivermectin, benzyl benzoate, permethrin, and sulfur ointment—for the treatment of scabies in a randomized controlled trial involving 200 patients.
DOI: 10.3109/09546634.2016.1151855 -
Comparative Study of Efficacy of Oral Ivermectin Versus Some Topical Antiscabies Drugs in the Treatment of Scabies
This study evaluates the efficacy and safety of oral Ivermectin compared to topical treatments such as Permethrin, Gamma benzene hexachloride, and benzyl benzoate for managing scabies, highlighting the need for effective community treatment options.
DOI: 10.7860/jcdr/2014/9092.4878 -
Scabies and Pediculosis Pubis: An Update of Treatment Regimens and General Review
An evidence-based update summarizing scabies and pediculosis pubis diagnosis and treatment regimens, highlighting ivermectin's efficacy, topical scabicides, resistance concerns, and population-level outbreak management.
DOI: 10.1086/342102 -
Comparison of safety, efficacy, and cost effectiveness of benzyl benzoate, permethrin, and ivermectin in patients of scabies
This study compares the efficacy, cost-effectiveness, and safety of three antiscabetic treatments—benzyl benzoate, permethrin, and ivermectin—in patients with scabies in Nagpur, India, revealing that while ivermectin has the highest cure rate, benzyl benzoate is the most cost-ef…
DOI: 10.4103/0253-7613.48882 -
Efficacy and side effects of Blacksoap® as adjuvant therapy of scabies: a randomized control trial
A single-blind randomized controlled trial in an Indonesian boarding school evaluated whether adding Blacksoap® to standard permethrin therapy for scabies improves cure rates, pruritus, and skin barrier (TEWL) compared with placebo (baby soap); no significant differences were ob…
DOI: 10.13181/mji.oa.225965 -
Bullous Scabies Mimicking Bullous Pemphigoid
This study presents a case of bullous scabies that mimicked bullous pemphigoid, highlighting the challenges in diagnosis and the successful treatment with permethrin after corticosteroids failed.
DOI: 10.1111/j.1346-8138.2003.tb00460.x -
Scabies increased the risk of chronic kidney disease: a 5‐year follow‐up study
In a population-based Taiwanese cohort, scabies infection was associated with a 34% increased risk of developing chronic kidney disease (CKD) over five years, with higher risk in men than women, based on matched controls and Cox regression.
DOI: 10.1111/jdv.12099 -
Treatment with ivermectin reduces the high prevalence of scabies in a village in Papua New Guinea
This study demonstrates that a single-dose mass treatment with ivermectin significantly reduces the prevalence of scabies in a village in Papua New Guinea.
DOI: 10.1016/s0001-706x(99)00087-x -
Measure To Control Of Parasitic Infections of Swine in Commercial Farm
Integrated biosecurity measures, regular on-farm parasitological diagnostics, and ivermectin- and amprolium-based antiparasitic therapy dramatically reduced major parasitic infections across production stages on four commercial swine farms, with six-month follow-up showing large…
DOI: 10.23880/izab-16000467 -
Utilization of Human Skin Equivalent in Research of Scabies Pathogenesis
Human skin equivalents reveal how live Sarcoptes scabiei infestation modulates cytokine secretion, adhesion molecule expression, and gene expression, illustrating HSE as a relevant in vitro model for scabies pathogenesis research.
DOI: 10.37010/nuc.v1i1.63 -
Barriers and challenges of returning patients back to community after renal transplantation in Central Australia
A retrospective study from Central Australia quantifies the length of stay in Alice Springs after renal transplantation and identifies medical and psychosocial barriers that delay returning patients from remote communities to their homes, highlighting modifiable and non-modifiab…
DOI: 10.1111/imj.15196 -
Heterologous expression and secretion of a Streptomyces scabies esterase in Streptomyces lividans and Escherichia coli
Clones Streptomyces scabies esterase and shows secretion of a mature enzyme in Streptomyces lividans and periplasmic secretion in Escherichia coli, with zinc induction boosting expression and the signal peptide being essential for secretion.
DOI: 10.1128/jb.174.8.2431-2439.1992 -
Outcomes of the California Ban on Pharmaceutical Lindane: Clinical and Ecologic Impacts
A multidisciplinary evaluation of the environmental and clinical effects of California's ban on pharmaceutical lindane, showing significant reductions in wastewater concentrations and unintentional exposures, with minimal negative impact on treatment practices for head lice and …
DOI: 10.1289/ehp.10668 -
Scabies associated with a bullous pemphigoid-like eruption
This case report describes a 36-year-old woman who developed a bullous pemphigoid-like eruption associated with scabies, highlighting the potential for scabies to mimic autoimmune blistering disorders.
DOI: 10.1111/j.1365-2133.1993.tb15155.x