Scabies is a skin condition caused by a mite, Sarcoptes scabiei, also called the “human itch mite.” It is a tiny, 8-legged bug, only visible under a microscope. A female mite will burrow into the outer layer of skin, called the epidermis, to live and lay eggs, which hatch within a few days, and the mites live and reproduce in the skin. Scabies causes intense itching, which is more common at night, a papular (“pimple-like”) rash, and sometimes small, blister-like “tunnels” that are visible on the skin. This rash is common in skin folds in the body, where the mites are more likely to burrow, such as in the armpits, groin, genital area, waist, insides of the wrists and elbows, buttocks, chest/nipple area, soles of the feet, and in between the fingers and toes. In babies and young children, it is also common on the face, neck, scalp, and palms of the hands. In some cases, “crusted scabies” can occur, which is an over-infestation of mites, causing red, scaly patches all over the body. This usually occurs in patients with suppressed immune systems. Scabies infection requires treatment with a “scabicide” medication, which is usually a topical prescription cream, and sometimes an additional oral medication.
Permethrin is a prescription cream that is applied to the entire body, left on for 8-14 hours, then washed off. Often, you will need to do another application, one week after, to successfully treat scabies. It is the treatment of choice and is approved for use in anyone over 2 months old, including pregnant women. It is a man-made pyrethrin, which is an insecticide that is naturally occurring in chrysanthemum flowers. It works by killing the mites and their eggs. It is important to note that permethrin is also available as a topical shampoo/solution for lice treatment. This is a lower concentration than permethrin cream and is not effective for scabies.
Lindane is a prescription lotion that is only recommended when scabies treatment with permethrin or other medications has not been effective. It is an organochloride, which is used in chemical pesticides, and can be toxic, especially to the nervous system/brain. Lindane use is not recommended in people with seizure disorders, infants and children, the elderly, pregnant or breastfeeding women, people weighing less than 50 kilograms, or in scabies patients with open sores or very irritated skin, due to the risk of toxic effects.
Sulphur is used in a prescription ointment to treat scabies and is the treatment of choice for infants younger than 2 months old. It is applied at night, left on for up to 24 hours before washing off, and can be used up to 5 days in a row for effective treatment. It is considered one of the safest treatment options, but the odour associated with sulphur can be unpleasant.
Ivermectin is an oral medication used for many other parasitic infections that is usually very effective in treating scabies. It is recommended in patients with scabies cases that are not cured by topical treatment such as permethrin, or cannot tolerate a topical treatment. It is given as two single weight-based doses, one week apart. However, it is not recommended for small children or pregnant women. Ivermectin is recommended in addition to topical treatment in patients with crusted scabies.
Crotamiton is an older topical medication for the treatment of scabies in adults. It requires 4 total doses and is not as effective as other topical treatments but is an option for patients who may have a sensitivity/allergy to other treatments.
Malathion is a prescription topical lotion typically used for lice, but it is sometimes recommended as a scabies treatment as well. It is an organophosphate used in some pesticides that kills scabies mites and their eggs. It is considered generally safe at the concentration used in prescription treatments. It is flammable so you should avoid open flames or very hot appliances when using this medication.
Benzyl Benzoate is a topical prescription solution recommended for severe cases like crusted scabies. It is a chemical that kills scabies mites and their eggs, which can be quite irritating to the skin. It usually works in one or two applications and can be used in a weaker concentration on children.
In addition to treatment with a scabicide, a topical steroid or antihistamine cream such as hydrocortisone or diphenhydramine, or an oral antihistamine such as hydroxyzine or diphenhydramine may be recommended to relieve itching and redness associated with scabies infection. In some cases, a topical or oral antibiotic medication may be needed to treat a bacterial infection associated with excessive scratching of scabies lesions.
Associated with scabies treatment medications usually only involve the skin. These include redness, stinging or burning, and itching where the medication has been applied. Most topical medications should not be applied to open sores or near the eyes, nose, mouth, or other openings on the body to minimize irritation and absorption into the body. If product gets into the eyes, they should be rinsed out with clean water immediately.
Signs of toxicity that require medical attention include nausea/vomiting, dizziness, rapid heartbeat, clumsiness, muscle cramps, and seizures. This is rare.
Scabies is very contagious and can be passed from person to person by direct skin-to-skin contact, or from infested clothing or bedding. In adults, it is often transmitted by sexual contact. It is common in crowded living conditions but is not usually due to poor hygiene. The rash and itching due to scabies are an allergic reaction to the mites’ proteins and faeces and may not appear for several weeks after infestation in an initial/first infection. However, scabies is contagious before the rash and itching appear. Therefore, it is important that any close contacts of a person infected with scabies are also treated. In addition to medication treatment, any clothing or bedding, or stuffed toys should be washed in hot water and dried in hot air in a dryer, or placed in a sealed bag or container for at least 72 hours to kill the mites. The living area should also be vacuumed and cleaned thoroughly during and after treatment.