Scabies is a highly contagious skin condition caused by the Sarcoptes scabiei mite. The infestation leads to intense itching, red bumps, and a distinctive rash as the female mites burrow under the skin to lay eggs. Eradicating the mites and their eggs requires specific medications, available only by prescription. Your healthcare provider will determine the most appropriate treatment plan for your specific situation.
First-Line Treatment: Permethrin Cream
Permethrin 5% cream is the most commonly recommended medication for scabies. It is considered a first-line treatment because it is highly effective and generally safe for most patients, including pregnant women and children over two months old.
How to use permethrin cream
Proper application is critical for successful treatment. The cream must be applied to cool, dry skin according to your doctor's instructions. Here is a general overview of the typical application process:
- Massage a thin layer of the cream into all skin surfaces as directed by your healthcare provider.
- Pay special attention to areas like between fingers and toes, under fingernails, armpits, and groin.
- For infants and the elderly, application may also include the scalp, hairline, temples, and forehead, as advised by a doctor.
- The cream is left on for a specific duration, typically overnight, before being washed off thoroughly with a bath or shower.
- Your doctor will advise if a second treatment is necessary and when it should be applied.
Oral Alternative: Ivermectin Tablets
For some patients, an oral medication may be necessary. Ivermectin is a pill that can be used to treat scabies, particularly in cases of crusted scabies, large institutional outbreaks, or when topical treatments fail. In the United States, oral ivermectin is not specifically FDA-approved for scabies but is used off-label.
When is ivermectin used?
- Crusted Scabies: This severe form of scabies involves a very high mite load and often requires a combination of oral ivermectin and topical permethrin.
- Institutional Outbreaks: In settings like nursing homes, oral treatment is easier to administer to a large group of people simultaneously.
- Immunocompromised Patients: Individuals with weakened immune systems may benefit from systemic treatment.
How Scabicides Work to Eliminate Mites
Scabicides are antiparasitic agents that specifically target and kill the scabies mites and their eggs, though some, like ivermectin, are not ovicidal. The primary mechanism for both permethrin and ivermectin is neurological.
- Permethrin: This synthetic pyrethroid paralyzes and kills the mites and their eggs by disrupting their nerve and muscle function.
- Ivermectin: This oral medication works by interfering with the nerve and muscle functions of the parasitic mites, leading to paralysis and death.
It is important to remember that itching can persist for several weeks after successful treatment. This is a hypersensitivity reaction to the remains of the dead mites and does not necessarily indicate treatment failure. Your doctor may recommend antihistamines or corticosteroid creams to manage the residual itching.
Addressing Crusted (Norwegian) Scabies
Crusted scabies is a severe and highly contagious form of infestation characterized by thick crusts of skin containing millions of mites and eggs. It typically affects individuals with weakened immune systems. Treatment for crusted scabies is more aggressive and typically involves a combination of topical and oral therapy. A regimen for crusted scabies might include:
- Repeated applications of topical permethrin cream as prescribed.
- Multiple doses of oral ivermectin, often taken days apart, as directed by a healthcare provider.
- Application of keratolytic creams to help remove the thick crusts and allow the medication to penetrate the skin more effectively.
Comparison of Key Scabies Medications
| Feature | Permethrin (5% Cream) | Ivermectin (Oral Tablet) | Sulfur (5-10% Ointment) | Spinosad (0.9% Topical) |
|---|---|---|---|---|
| Application | Topical cream | Oral tablet | Topical ointment | Topical suspension |
| Application Frequency | Typically one or two applications, as directed | Two doses often recommended, as directed | Applied as prescribed by a doctor | Applied as directed by a healthcare professional |
| FDA-Approval for Scabies in the U.S. | Yes | No (used off-label) | Yes (compounded) | Yes (for ages 4+) |
| Best for | Classic scabies, first-line treatment | Crusted scabies, institutional outbreaks | Infants <2 months old, pregnant women | Patients 4 years and older |
| Kills Mites & Eggs | Yes | Mites only (not ovicidal) | Yes | Yes |
| Key Considerations | Safe for most patients, including pregnant/nursing women | Not for children <15kg, pregnant/nursing women | Unpleasant odor, messy application | FDA-approved in 2021, limited comparative data |
Other Treatment Considerations
- Environmental Decontamination: All clothing, bedding, and towels used within three days of treatment must be washed in hot water and dried on a hot cycle. Items that cannot be washed should be sealed in a plastic bag for at least 72 hours.
- Treating Contacts: All close contacts, including household members and sexual partners, should be treated at the same time to prevent re-infestation, even if they don't have symptoms.
- Managing Symptoms: Itching and other symptoms may persist for up to a month. Over-the-counter antihistamines or prescription steroid creams can help manage these symptoms.
Conclusion: Choosing the Right Treatment
While there is no single drug that kills scabies universally, the most common and effective prescription medication is permethrin cream, which kills both the mites and their eggs. For severe cases, institutional outbreaks, or those who cannot use topical creams, oral ivermectin is a powerful alternative. Both treatments should be used as directed by a healthcare professional, with all close contacts treated simultaneously to prevent reinfection. For severe infestations like crusted scabies, a combination of both oral and topical therapies is often necessary. Always consult a doctor for a proper diagnosis and the most suitable treatment plan to ensure effective eradication of the mites.
For more detailed information on scabies and its treatment, you can visit the Centers for Disease Control and Prevention's website.
