Crusted Scabies – Know the causes, symptoms, and treatment

Have you ever wondered what would happen if scabies is left untreated? Well, it can slowly but eventually turn into the severe and rare form of scabies – the crusted or Norwegian scabies. This is an extremely contagious hyperinfestation with Sarcoptes scabiei var hominis.

Crusted Scabies - Know the causes, symptoms, and treatment

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This form of scabies may occur in:

People with the weak immune system due to some nutritional disorders, infectious diseases, leukemia, or weakened immune systems (such as people who have AIDS).

Even people suffering from mental or nervous system disorders may be infected with this form. As in the beginning, the itching sensation caused by scabies may be masked in these patients. When scabies goes undetected in these patients for a very long time, the infestation may become severe leading to crusted scabies.


In certain immune-compromised patients, the signs of scabies may be misdiagnosed as psoriasis or seborrhoeic dermatitis. Due to this, the actual treatment is not followed up for the patients and it further results in forming crusted scabies. People with crusted scabies may have up to 4,000 mites living on their skin and these mites may even grow over to 1 million. Just imagine how easily these patients can spread the mites to non-infested people.

How scabies is passed

Scabies is passed on from infested individual to a non-infested one through skin-to-skin contact or by using their personal belongings like bed sheets, towels or clothes. The crusted scabies occur is people that don’t have a strong immune system to fight these mites. 

Following are the risk factors for crusted scabies:

  • Increased age
  • Down syndrome
  • Dementia
  • Leprosy
  • Human immunodeficiency virus infection (HIV)
  • Lymphoma
  • Systemic lupus erythematosus (SLE)
  • Long-term use of corticosteroid or immunosuppressant

What causes crusted scabies?

The exact reason why crusted scabies occurs is not known but it is associated with increased levels of eosinophils, IgE and IgG. In this condition, the dermis is infiltrated with lymphocytes and eosinophils. This further increases ratio of CD8 and lymphocytes as compared to a normal person.

What are the clinical features of crusted scabies?

Some poorly defined red patches may develop on your skin and later these patches may turn into thick scaly plaques in-between fingers, under nails, and over soles and palms. It may also affect elbows and knees. In this severe form of scabies, mites are also present in nail beds and may cause splitting of nail plates.

There is minimal or no itching at all in crusted scabies. This happens due to the decreased immune response of a body. The following factors may decrease symptoms of itching or urge of scratching:

  • Physical limitation
  • Muscular atrophy
  • Neuropsychiatric disorders
  • Loss of cutaneous sensation
  • Osteoarticular deformities

Some complications that are associated with crusted scabies include:

  • Infestation of numerous contacts, including family and staff members
  • Secondary bacterial infection


This form of scabies is diagnosed clinically – just like regular scabies – with an identification of mites or eggs on dermatoscopic or microscopic examination of burrows. Even reflectance confocal microscopy can be used to examine burrows, mites, eggs, and feces.


Here the treatment regimen for scabies and it should be applied every second day and then twice a week to get rid of crusted scabies:

  • Permethrin 5% cream or benzyl benzoate 25% emulsion for patients over 6 months of age
  • Crotamiton 10% is used for infants under 6 months
  • In addition, 5% tea tree oil or sulfur ointment can be used

Keratolytic creams are prescribed for scaly plaques. First, you need to soften the crust in warm water and then apply the following:

  • Salicylic acid 5% to 10% in sorbolene cream
  • Lactic acid 5% and urea 10% in sorbolene cream

Combination treatment recommended by US Centers for Disease Control (CDC):

  • Topical 5% permethrin or topical 5% benzoyl benzoate applied for a week, and
  • Oral ivermectin must be given on days 1, 2, 8, 9, and 15. This can be repeated if the condition is severe.


What is norwegian scabies

Skin problems and treatments

Crusted scabies 

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