What is scabies?
Commonly called the “itch,” scabies is caused by a tiny eight-legged mite named Sarcoptes scabiei. The male and female mite will mate on the skin surface, after which the fertilized female quickly burrows under the skin to begin deposition of her eggs; a process that can result in laying from 10-25 eggs over a period of 1-2 months. The female eventually dies in the extended burrow she created. Her larvae will hatch 3-4 days after being deposited and the mites will travel to the surface of the skin where they mature, and the process will be repeated. The intense itching is caused by the body's allergic reaction to the mite, their eggs, and their feces.
What are the signs and symptoms of scabies infestation?
Small (1-2 mm diameter) red scabbed bumps, sometimes with associated burrow markings that are located in one or more of the following areas: sides and web spaces of the fingers, the flexor aspects of the wrists, the extensor aspects of the elbows, anterior and posterior axillary folds, periumbilical region, anterior and lateral waistline, the extensor surface of the knees, the lower portion of the buttocks and nearby area of thighs, and the lateral sides of the feet. In females the area adjacent to the nipples, and in men the genitalia may be affected. The back is typically non-involved; the head is generally spared in adolescents and adults.
Intense itching is the most frequent complaint; typically worsened at night and often over much of the body. Excoriation sores on the body may be caused by scratching. The sores sometimes become secondarily infected with bacteria due to incessant scratching.
How is scabies transmitted?
Scabies is not an indication of bad hygiene or nutritional deficiency. It is transmitted by direct, prolonged, skin-to-skin contact with a person already infested with scabies. (A quick handshake or hug will usually not spread infestation.) Scabies is commonly spread to sexual partners, family members, schoolmates, teammates, and roommates. Infestation may also occur by sharing contaminated clothing, towels and bedding. Pets do not typically spread scabies to humans. The scabies mite that affects animals is different than the human scabies mite. The scabies mite that affects animals cannot survive or reproduce on humans, so although they can cause temporary itching and rash, they will not cause a full-blown infestation.
How long after exposure will symptoms begin?
For a person who has never been infested with scabies, symptoms may take 4-6 weeks to begin. For a person who has previously had scabies, symptoms appear within several days, likely due to sensitization of the immune symptom at time of earlier infestation. You do not become immune to subsequent infestations.
How is scabies diagnosed?
Diagnosis is most commonly made by a visual examination of the skin looking for burrows or rashes typical of a scabies infestation. A skin scraping may be performed by your provider, followed by microscopic identification of the specimen if the diagnosis remains unclear. They will look for mites, eggs or mite fecal matter to confirm the diagnosis.
Treatment of Scabies
Currently the most effective treatments are Permethrin 5% Cream (Elimite or Acticin) or Lindane 1%. Permethrin is least neurotoxic and is safe for adults, adolescents, infants, children and even pregnant women, and therefore generally tried first. Always follow the directions provided by your physician or the directions on the package insert. Massage the cream into your skin from the neck down to the toes and include the soles of your feet. Leave on for at least 8 hours (but no longer than 14 hours), then take a bath or shower to wash off the medication. Put on clean clothes. One treatment with Permethrin typically eradicates all mites and eggs from the body. A variety of other medications besides Permethrin are available for treatment of scabies, however, due to potential side effects and cautions, these warrant further conversation with your healthcare provider to assure they are safe for you. Itching may take several days or even weeks to resolve completely even after effective treatment and eradication of the mites and eggs. Antihistamines (such as Benadryl/diphenhydramine or Zyrtec/cetirizine) and over the counter 1% hydrocortisone cream may help reduce itching. Antihistamines can cause drowsiness which needs to be taken into consideration with concurrent use of other sedating medications, driving, and the use of alcohol or recreational drugs. Topical steroids should be used strictly per label medication instructions to avoid potential for permanent weakening of skin integrity. To decrease the likelihood of re-infestation, any clothing or bed linens used in the past 4-5 days should be washed in hot water and dried in a hot dryer. Any item that cannot be washed should be placed in a sealed, plastic bag for at least a week to make sure to kill any mites on the object.
Who should be treated?
Anyone diagnosed with scabies, their sexual partners, and persons who have close skin-to-skin contact or frequent sharing of clothing/bedding should be simultaneously treated. It is rarely necessary to repeat the treatment, but if new evidence of scabies or a spreading rash is noted 2 weeks after initial treatment, one should consider re-treatment.
For more information, visit the CDC website.