Dr Prajwal Pudasaini, MD, a dermatologist at Civil Service Hospital, elucidates the causes and treatment of scabies and debunks some myths surrounding this skin infection.

What is scabies, and what causes it?

Scabies is a common infectious, parasitic skin infection caused by mites named Sarcoptes scabiei var hominis. It’s highly contagious and is transmitted through closed contacts, sexual activity, and sharing clothes with those infected.

Why are they primarily itchy at night?

One of the most common presenting features is “itch” in scabies, which is nocturnal and most severe at night because the mite is more active at that time and tends to be motile, excavating the skin layers at night. The mite allergen induces a hypersensitivity reaction, causing severe itch in patients. The itchiness can be controlled through prompt diagnosis and adequate treatment of patients and household contacts.

How common is scabies, and are there any people particularly at risk?

Scabies is a commonly encountered skin infection and a major public health concern in many tropical regions, including Nepal. The prevalence of scabies worldwide is around 300 million, with a significantly high number of cases in South-East Asia. In Nepal, the prevalence of scabies is around 5.5%. It mostly affects children, adolescents, and the elderly.

Scabies predominates in people of lower socioeconomic strata, in impoverished regions, in overcrowded living conditions, in lack of health and hygiene, malnourished and those with immunodeficiency including HIV and AIDS.

What are the primary symptoms of scabies?

The primary symptom of scabies is an itchy rash over typical sites, which is worse at night. These rashes can be modified by repeated scratching by patients in response to the intractable itch, later presenting as erosion/ excoriation and secondary infection. There’s almost always a history of scabies in close contacts, such as family members, sexual partners, or friends sharing bedding/apparel in hostels.

These clinical features are peculiar to scabies and can be differentiated from other skin diseases with similar manifestations.

Are there specific areas of the body more prone to scabies?

Certain parts of the body are more prone to develop the primary rash of scabies, such as the wrist, finger webs, axillae, and trunk- in the suprapubic region/ periumbilical region, thighs, buttocks, breast in females, penis and scrotum in males.

Adults usually spare the face and neck because the large number of sebaceous glands in these sites act as a natural scabicidal agent, thereby preventing the mite from developing and excavating the skin of the face.

How are scabies diagnosed, and what are the most effective treatments for it?

Scabies is typically diagnosed based on their characteristic signs, such as intense itching at night, involvement of common areas like the scrotum or penis in males, and breasts in females, along with a history of scabies in close contact. Additional tests like dermoscopy or microscopy can help confirm the diagnosis.

The most effective treatment modality is to use permethrin 5 % lotion overnight and repeat it after a week. It is to be used with a doctor’s prescription and advice only. One can also use an oral Ivermectin tablet (also repeated in a week), as prescribed by the doctor, as it should be avoided in pregnant females, children less than 5 years and those with seizure disorder.

What can be done to prevent it from spreading?

Scabies are highly contagious and can be seen to spread in huge numbers of people and their close contacts in hostels, hospitals, elderly homes and migrant/refugee camps.

The spread of scabies can be prevented by avoiding close/ physical/ sexual contact with those infected with scabies, good personal hygiene, not sharing beddings/ clothing of the infected, proper and adequate treatment of those infected and public awareness about the infectivity and contagiousness.

Can someone develop immunity to scabies after an infestation, or is reinfection possible?

Although scabies infection tends to develop an immune response, these antibodies are not protective, and reinfection can still occur, with recurrences in the immunosuppressed.

Are there any common myths about scabies that you’d like to debunk?

Myth: Scabies can be acquired or transferred to and from household pets.

Reality: The particular species that infest humans, Sarcoptes scabiei var hominis, occurs only in humans and isn’t acquired from pets or transferred to them from humans.

Myth: Thousands of mites crawl into our bodies during the itch.

Reality: The itch that is out of proportion to the visible rash is due to a hypersensitivity reaction to mite antigen, not thousands of mites crawling and excavating our skin.