Permethrin cream is a topical medication essential for treating scabies and head lice infestations. The active component, permethrin, is a synthetic chemical derivative of pyrethrins, which are natural compounds from the chrysanthemum flower. Permethrin falls under the pyrethroid class, mimicking natural pyrethrins but with greater stability and longevity. This chemical targets the nerve cells of parasites, disrupting sodium ion channels, which leads to their paralysis and death. Rapidly metabolized in humans, permethrin presents minimal systemic exposure, rendering it safe for external topical application on the skin.
Historical Use and Approval
Developed in 1973, permethrin’s potent insecticidal properties soon transitioned from agricultural uses to pharmaceutical applications, particularly in public health for controlling parasitic skin infestations. The U.S. Environmental Protection Agency registered permethrin for use in 1979, and shortly after, it was approved by the U.S. Food and Drug Administration for topical use against scabies and lice. This marked a pivotal moment in medical history, positioning topical permethrin alone as a preferred method for treating these common yet distressing conditions.
Permethrin cream rapidly became the treatment of choice for scabies, caused by mites burrowing into the skin, and for lice, spread through close contact or shared personal items. Its efficacy and safety profile made it superior to previous treatments, offering relief with minimal risk of side effects, such as mild skin irritation, which are generally transient and resolve without further intervention.
The approval and widespread adoption of permethrin in healthcare reflect its significance in managing dermatological parasites safely across various populations, including adults and children over two months of infant or young child of age. Its environmental and mammalian safety further underscore its sustainability, making it a staple in both medical and agricultural settings.
Through years of clinical use, permethrin cream has proven to be a cornerstone in treating parasitic infections, continuing to play a critical role in global health initiatives. Its development from a synthetic chemical to a mainstay in treating parasitic skin conditions illustrates the ongoing impact of innovative chemical research in public health.
Uses of Permethrin Cream
Treating Scabies
Scabies is an infestation caused by the scabies mite that results in severe itching and rash due to allergic reactions to the mites burrowing in the skin. Permethrin cream is highly effective in treating scabies; it is applied as a thin layer over the entire body, from the neck down, and left on for a prescribed period before being washed off. This treatment may be repeated after a week to ensure that all mites and their eggs are eradicated. Scabies rarely infests the scalp of adults and older children, but the hairline, neck, temples, and forehead may be affected in younger children and infants.
Treating Head Lice
Permethrin lotion, another form of the medication, is used to treat head lice. Similar to its use in treat lice and scabies, the lotion is applied to the affected area—typically the scalp—and left on for about 10 minutes before being rinsed off. This treatment kills the lice and their eggs effectively. Care should be taken to treat all infected persons and their close contacts simultaneously to prevent re-infestation.
Preventing Reinfection and Spread
Permethrin cream can also play a crucial role in preventing the spread of infestation among close contacts and sexual partners, particularly because scabies and head lice can be transmitted through direct physical contact. Clothing, bed linen, and towels used by an infected person should be washed in very hot water and dried on a hot cycle to kill any mites or lice that may have transferred. Items that cannot be washed may be sealed in a plastic bag for a couple of weeks to ensure all mites and lice are dead.
How Permethrin Cream Works
Permethrin cream acts by disrupting the function of the neurons in parasites, causing paralysis and death—a mechanism that is effective against both mites and lice. When applied as directed, permethrin binds to the skin and hair follicles, from where it is slowly absorbed into the whole body, to exert its effect. This targeted approach ensures that the medication acts directly where the parasites thrive, while its minimal absorption into the human body keeps unwanted effects at bay.
For the treatment of scabies, a single application of permethrin cream may suffice, but depending on medical advice, a second treatment could be necessary to handle any residual mites that survived the first treatment. The cream should be applied all the same way over the body from the jawline downwards, and special attention should be given to creases in the skin, between fingers and toes, and under the nails where mites tend to hide.
The effectiveness of permethrin in treating scabies and lice is generally high, with the cream able to kill mites used to treat scabies and lice soon after application. However, the itching may continue for several weeks after successful treatment due to an allergic reaction to the dead mites, not necessarily indicating an ongoing infestation. For persistent symptoms, further medical attention should be sought.
Permethrin cream’s role in public health, and medicine, particularly in controlling outbreaks in communities and healthcare settings, cannot be overstated. Its ability to break the cycle of infection and re-infection makes it a vital tool in managing outbreaks of scabies and lice, diseases that, while not typically associated with serious health issues, can cause significant discomfort and social stigma.
How to Use Permethrin Cream
Proper Application
When using permethrin cream to treat scabies or lice, it’s crucial to follow the instructions on the prescription label or those provided by a healthcare professional. The cream is generally applied to clean, dry skin. For treating scabies, apply a thin layer of the cream over the entire body, paying particular attention to creases and areas where mites are likely to hide, such as between the fingers and toes, under the nails, and on the genitals. For infants and young children, treatment should also include the head and scalp since these areas are more commonly affected in younger patients. The cream should be left on for 8 to 14 hours, usually applied at bedtime and washed off in the morning.
For treating head lice, apply the permethrin lotion to the hair, ensuring that all hair is thoroughly wet with the lotion. After application, leave the lotion on for about 10 minutes before rinsing it off with warm water.
After Treatment
After the cream has been washed off, all clothing, bedding, and towels used by the treated individual during the infestation and treatment period should be washed in hot water and dried on a hot cycle to kill any remaining mites or lice. Items that cannot be washed should be sealed in a plastic bag and stored away for at least two weeks to suffocate any remaining parasites.
Reapplication
Depending on the severity of the infestation and the healthcare provider’s advice, a second application of permethrin cream may be necessary about a week after the first to ensure all mites and their eggs are eradicated. Always consult with a healthcare provider before reapplying permethrin to young child to avoid unnecessary exposure to the medication.
Possible Side Effects
While permethrin cream is generally safe and effective when used as directed, it can cause side effects in some individuals. Common side effects include mild burning, stinging, itching, or redness at the application site. These symptoms usually subside as the body adjusts to the treatment. However, if these effects persist or worsen, it’s important to seek medical attention.
Allergic Reactions
Though rare, some people may experience a severe allergic reaction to permethrin. Signs of an allergic reaction include rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, or trouble breathing. If any of these symptoms occur, medical help should be sought immediately.
Long-term Exposure Concerns
Excessive application or inappropriate use of permethrin cream can increase the risk of side effects. Studies in animals have shown that very high doses of permethrin can affect reproductive function and increase the risk of liver changes like benign liver adenomas and pulmonary adenomas. However, the concentrations applied permethrin used in topical treatments for humans are much lower, posing minimal risk when used as directed.
Precautions and Warnings
Age Considerations
Permethrin cream is approved for use in adults and children over 2 months of age. However, it should be used with caution in young children and infants due to their skin’s greater permeability and potential for increased absorption of the cream.
Drug Interactions and Health Conditions
Before using permethrin, it’s important to inform your doctor about any other medicines you are taking, including prescription, over-the-counter, vitamins, and herbal products, as there can be interactions. Also, inform your doctor or healthcare provider about any existing skin conditions or allergies to avoid adverse effects.
Environmental Precautions
Permethrin cream should be kept away from direct light and stored at room temperature. The cream should not be disposed of in waterways as it can be toxic to aquatic life.
Sexual Partners and Close Contacts
Since scabies and lice can be easily sexually transmitted infections through close physical contact, it is recommended that sexual partners and other close contacts of an infected person be treated simultaneously to prevent re-infestation.
Follow-Up
Follow-up with a healthcare professional is crucial to ensure the treatment has been effective and to address any complications from the infestation or treatment. If symptoms persist weeks after treatment or if new symptoms develop, further evaluation and treatment may be necessary.
By adhering to these guidelines, individuals can use permethrin cream safely and effectively, minimizing the discomfort and spread of scabies and lice infestations.
Conclusion
Permethrin cream is an essential treatment for scabies and lice, offering effective relief from these uncomfortable and socially stigmatizing infestations. By targeting the nervous system of parasites, it ensures rapid and effective eradication when applied correctly. It’s crucial for both the affected individual and their close contacts, including sexual partners, to undergo treatment simultaneously to prevent re-infestation and manage outbreaks effectively. Users should adhere to medical guidelines, particularly regarding application and post-treatment hygiene, such as washing textiles in hot water. While typically well-tolerated, users should be vigilant for any side effects, especially allergic reactions, and seek medical advice if symptoms persist or worsen. Proper use of permethrin cream under medical supervision ensures a safe and effective resolution of these parasitic infestations.