A B C D E F G H I J K L M N O P R S T U V W

SCABIES

What is Scabies ?

Scabies is caused by the infestation of the skin with a small parasite called Sarcoptes scabiei . Once the scabies mite has established itself in the skin, it starts to reproduce. The proteins from the mite are absorbed through the skin, and after a period of 6 to 12 weeks, the body reacts by developing a highly itchy skin rash. This can affect the whole body from the neck downwards.

How does Scabies occur ?

Sarcoptes scabiei is transmitted by skin to skin contact with an infected individual. This can occur by pure physical contact, i.e. holding hands for 15 to 20 minutes, by hugging individuals or hugging or carrying children. It can be transmitted by sexual intercourse. Conventional scabies cannot be caught by contact with bedding or clothing. There is, however, a specialized form of scabies which can occur in patients who have low immune response or who have a neurological disease in which very large numbers of the mites accumulate in the skin. Unaffected individuals can catch conventional scabies by contact with skin scales or clothing from these individuals.

Why does Scabies occur ?

The itchy eruption association with scabies is not due merely to the presence of the scabies mite but is an immunological response to proteins produced by the mite that the body then reacts to. It takes the body 6 to 12 weeks to develop this immunological reaction. During this "window period", the individual is infectious but has no symptoms of itching. The mite itself localizes to very specific sites on the body and, in particularly, between the fingers and on the wrists, around the nipples in women and on the penis in men. Here they can be identified by tracks about 2 mm long, usually with a small blister at one end. The mite lives in these burrows, reproduces and immature mites then escape onto the surface to either reinfect the skin or to infect another person. The rash, when it develops, is due to the immunological or allergic response to the proteins produced by the mite. The characteristic distribution is over the elbows and knees, the lower back and shoulders. It may generalize and cover the whole body but never affects the head and neck in adults. In infants, the rash can affect the face and also the scalp. In infants and children it is quite common to find small pustules on the palms and soles in response to this infestation.

Treatment involved for Scabies

Treatment involves the application of a scabicide, i.e. an agent that will kill the mite over the entire body from the neck downwards. If infants are affected, then the face and scalp also needs to be treated. At present the first line treatment of choice is with lotions containing malathion but carbaryl and benzyl benzoate are also used. In infants, a cream containing sulphur tends to be the first line treatment of choice. The lotion must be applied from the neck downwards covering every part of the skin, usually in the evening before going to bed. It is very important to ensure that every part of the skin is covered, particularly between the buttocks, on the genitals, the soles of the feet, between the toes and between the fingers. The lotion needs to be left on the skin for 24 hours and, if you wash your hands, you need to reapply the lotion to the hands again. After 24 hours, bed linen should be changed and clothing that comes in intimate contact with the skin should also be laundered. Suits and dresses can merely be hung in the wardrobe for the next 24 hours, as the mite will die fairly quickly once it is taken away from the body. After 24 hours, a bath should be taken, washing the skin very carefully. It is very important that all members of a family and all persons that have had physical contact with you are treated at the same time. Remember that some persons may be infected but not itchy, and these individuals could transmit the infestation back to you once you have been treated.

During treatment for Scabies

Malathion tends to be very well tolerated, causing little irritation. Benzyl benzoate can, however, irritate the skin. If you become reinfected with the scabies mite, you will start itching within a few days of the infection. This is because the immune system is already primed for the mite and will respond more quickly the second time.

After Treatment

Irritation may persist for up to 2 weeks after the infestation has been eradicated. This can be treated with topical corticosteroids. On rare occasions, skin nodules may develop which are intensely itching and which may persist despite effective eradication of the infestation and even after the use of topical corticosteroids. These may occur on the arms and legs or on the penis in men. These may require injections of steroids into them to cause resolution, or may need to be surgically removed.

If Scabies is left untreated

The scabies mite will persist on the skin indefinitely if not treated adequately. This will lead to persistent irritation of the skin and to transmission to individuals who have close contact with the person infested.

Effects on family of Scabies

Scabies is highly contagious through physical contact. All members of a household who have physical contact and particularly family members including children must be treated at the same time, to eradicate the infestation. Different individuals will develop an itch at different times following the infestation, and it is therefore important to treat family members who are not itching, as well as those who are itching.