How do you know when scabies are gone? (+1 observations)

In this article, we will discuss the improvement in symptoms that verifies that you no longer have scabies and the parasitic infestation has subsided. We will also discuss different treatment plans used to cure scabies.

How do you know when scabies are gone?

If you no longer experience itching after the treatment then it means that your scabies are gone. You may also observe a reduction in both the number of lesions and the degree of pruritus (unpleasant feeling of wanting to scratch). The microscopic examination will also give a negative result (1).

You may experience persistent and intense itching during the first week of treatment. However, the symptoms will begin to improve after that. The rash will disappear within two weeks, while itching will go away within four weeks.

In some cases, the rash and itching may persist for several months due to an allergic reaction to the mite debris. In older children and adults, these rashes appear in the limb extremities and interdigital spaces (spaces that separate the fingers).

In infants and the elderly, it may also appear on the scalp, palms, and soles. Scabies are transmitted due to skin-to-skin contact with an infected person. The symptoms of scabies may appear after 4 weeks of initial infestation. However, symptoms reappear more rapidly after subsequent infestations.

What does research suggest?

In one of the case reports, a 3-year-old girl presented with itching, lesions (in the shape of papules), and skin-picking (excoriation). After the treatment with oral medication (ivermectin), and topical preparation (sulphur and crotamitone) the itching was reduced and the lesions were healed (2).

A 52-year-old female presented with a diffused, intensely pruritis rash with high blood pressure and lesions on the right breast. The pink nodules were also evident on the buttocks, groin, and abdominal region. After the treatment, her rash subsided within one month with no new visible lesions (3).

In one of the clinical studies, clinicians established that topical permethrin was more effective (98%) against the parasite as compared to oral ivermectin (70%). However, the patient (n=85) responded well to the second dose of ivermectin, and the cure rate improved to 95% (4).

In another study, clinicians established that ivermectin and permethrin were equally effective against the scabies mite at the end of the 4-week treatment regimen. Both drugs were administered at a dose of 200 µg/kg/dose (single or double) (1).

How do you know if scabies treatment failed?

After 4 weeks of treatment if you still experience the following symptoms then it means scabies treatment has failed:

• No improvement in pruritis and skin lesions,
• Persistent itching,
• Formation of new lesions which were not previously evident, and
• Microscopic analysis shows mites in cuticles.

How long do scabies typically last?

When you first scabies, you may not know about it for about a month that the parasites are burrowing in the cuticles. The number of parasites may increase to 25 in 50 days, and about 500 in 100 days. After this, the parasite rate begins to decline (4).

Mites may survive for 24-36 hours at room temperature and average relative humidity. In the case of crusted scabies, hyperinfestation of millions of mites may occur in the cuticle of a patient. However, such cases are rare.

When you get infected for the second time, you may begin to itch the site within 24 hours. The mite population rarely grows during the second infection. Scabies mites may live on the person for one to two months if not treated.

The immunity in the host develops due to three processes (5):

• Scratching: it mechanically removes the parasite,
• Oedema: prevents the colonization of parasites and forces them to leave their burrows, and
• Sepsis: Scratching also causes sepsis which is fatal for Sarcoptes.

What are the complications of scabies?

Although scabies itself is a highly contagious disease, it is often accompanied by secondary infection and post-infective complications. Scabies may also decrease the quality of life.

Secondary infection

The mite burrows may become infected with bacteria, especially Staphylococcus aureus and group A Streptococcus. These bacteria may cause superinfection. These infections can lead to glomerulonephritis, and rheumatic fever (6).

The secondary bacterial infection may also cause impetigo, furunculosis, secondary eczematization, and abscess formation. Secondary infections are more common in crusted scabies because they tend to spread rapidly.

Post-infective complications

Post-scabies syndrome may occur in some patients infested with mites. It is characterized by severe itch even when the scabies infestation has been treated. It occurs due to an allergic reaction to mite debris and may persist for several months.

Decreased quality of life

A person with scabies often experiences social stigma because of the skin lesions seen in the exposed areas. It may decrease the patient’s quality of life due to embarrassment. It also affects the sexual life and daily activities of the patient (7).

What is the treatment of scabies?

According to the World Health Organization, around 400 million people are affected by scabies every year. Scabies can be treated with different oral and topical medications.

Medication

The medication used in the treatment and management of scabies include (8):

• Topical permethrin: It stops the neurotransmission of arthropods by disrupting the voltage-gated sodium channels. It is supplied as a 5% topical cream.
• Topical Lindane: It causes parasite paralysis by causing neuronal hypersensitization. However, Lindane is known to cause neurotoxicity in the host, which led to its market removal in many countries.
• Oral ivermectin: It activates ligand-gated chloride ion channels that cause persistent depolization in the parasite.
• Sulphur ointment: It is often preferred in resource-poor areas because it is a cheap and affordable medication.
• Crotamitone: It is a scabicidal and general antipuritic agent used in the treatment of scabies through the topical route.
• Benzyl benzoate emulsion: These lotions are applied topically and act on the central nervous system of mites to destroy them.
• Antibiotics: They are prescribed if the patient has a secondary infection due to scabies. Flucloxacillin and cephalexin are the drugs of choice for these infections.

In some cases, amoxicillin, azithromycin, and trimethoprim-sulfamethoxazole may also be prescribed. Amoxicillin often gives an unusual urine odour, however, it is considered normal. 

Prevention and precautions

Scabies is a highly contagious disease. Some preventive actions to reduce the spread of scabies include:

• Avoid skin-to-skin contact with a person you may think has scabies or live an unhygienic life.
• Wash and dry the bedsheets that were used by the infested person.
• If one person has scabies in the house, all members should get check-ups and treatment for scabies to prevent the spread of parasites.
• Sweep the area clean where the infested person was residing.
• Pregnant women and children with a weight less than 15 kg should avoid oral ivermectin.

As a pharmacist, I would suggest you to keep your bedding hygienic especially if you visit developing countries. Always follow the dosing regimen suggested by your doctor for scabies treatment. Try not to scratch the rash as it increases the occurance of secondary infections.

References