How is scabies treated?

Your doctor will usually prescribe you a cream that contains an active ingredient called permethrin. To make sure that the cream reaches and kills all scabies mites and their larvae and eggs, it has to be applied carefully all over the body from the chin down, including behind the ears and on the back of the neck. Adults usually need at least 30 grams of the permethrin cream to cover all of their skin. That is either the whole tube or half of the tube, depending on the product. The skin should be kept dry for at least 30 minutes before using the cream, which must be applied to dry skin because it is less effective otherwise. It should be left to soak in for 5 to 10 minutes before you get dressed again. It is important to make sure that you don’t wash your skin after applying the scabies cream. If you do wash your hands, for instance, then you should re-apply the cream afterwards.

It is normally not necessary to apply the cream to your face and scalp. But it's often a good idea for children and people aged 60 and over to also apply it to their face and scalp, just leaving their mouth and eyes uncovered.

It is best to ask somebody to help you put the cream on places that are difficult to reach, like your back. They can wear disposable gloves to avoid infection.

The permethrin cream has to be left on for at least 8 hours, but preferably 12 hours, so it's best to put it on in the evening. It is important to change your bedding before you go to bed, and again the next day too. Once the cream has been left to take effect over night, you can shower and wash as normal the next morning.

A single treatment is usually enough. But experts now recommend repeating the treatment after seven to ten days. This repeat treatment is particularly important if

• the scabies is very severe,
• you have a weakened immune system,
• several people from the same group of contacts are affected, like in a care home, or
• maybe not enough cream was applied to all areas of skin the first time around.

Treatment with permethrin cream helps in most people. A number of studies have found that the treatment got rid of scabies mites in up to 90 percent of those who used it.

If scabies mites do survive, it may be because they are more resistant to the active ingredient. But there are more common reasons why the treatment isn’t effective, such as

• the cream wasn’t applied all over, or not enough cream was applied,
• the recommended additional measures weren't taken,
• close contacts weren't treated at the same time, or
• you were infected again straight after the treatment.

The treatment is well tolerated overall. The possible (but rare) side effects of permethrin cream include irritated skin, feelings of cold or warmth, temporarily increased itching and (very rarely) allergic reactions.

Permethrin creams aren't the only scabies medications that are applied directly to the skin (topical medications). The other options contain either crotamiton or benzyl benzoate. These active ingredients are also effective scabies treatments. But they have to be applied on three to five days in a row and be left on the skin the whole time. That makes treatment with these medications more complicated. They are recommended if permethrin creams can't be used, for instance because of allergies.

Ivermectin tablets are an option if treatment with permethrin cream isn't possible or hasn't helped. Some people are advised to take tablets without trying the cream first, for example because they have a weakened immune system or aren't able to apply the cream all over due to a disability. Like permethrin, ivermectin is only available on prescription from the pharmacy. The dose depends on the person’s body weight:

• One tablet contains 3 milligrams of ivermectin.
• 3 milligrams of ivermectin (1 tablet) have to be taken per 15 kilograms of body weight.

So, for example, someone who weighs 75 kg will need 15 milligrams. That is the amount in 5 tablets.

All tablets are taken at the same time, ideally on an empty stomach, so at least two hours after eating. You then have to wait another two hours before eating again. The active ingredient travels around the body and reaches the layer of skin where the scabies mites live.

Ivermectin kills the mites but not their eggs. Because of this, people are advised to take the tablets again seven to fourteen days later. The second round of treatment then kills the young mites that have hatched from the eggs.

Ivermectin tablets are generally well tolerated. Possible (but rare) side effects include temporarily increased itching, headaches, nausea, allergic reactions, and liver problems.

The itching and rash often last for a few weeks after the treatment, even if the treatment was successful. That is not unusual, but can be unpleasant. The following things might then help:

• Skincare products such as light moisturizing creams and lotions can stop the skin from drying out and then itching even more.
• Antihistamine tablets can also relieve the itching.
• Inflammation-reducing steroid creams are recommended for severe rashes.

If the itching persists, it's a good idea to keep your fingernails cut short and filed down straight to make sure you don't scratch your skin open.

Permethrin cream is typically used to treat scabies in children and teenagers, too. But it has not been approved for use in babies under the age of three months. You can then talk to the doctor about whether it might still be possible to use this drug anyway ("off-label" use). Alternatively, crotamiton creams can be used in babies and children, and children over one year old can use benzyl benzoate creams. Closer medical supervision of the treatment is recommended. Because of this, babies usually have the treatment in hospital, and toddlers sometimes do too. Ivermectin tablets have not been approved for use in children who weigh less than 15 kilograms.

There are no approved scabies medicines for pregnant women and nursing mothers. Here again, they can talk to their doctor about the possibility of using permethrin cream off label.

Most people who have scabies only have a few mites on their body. People with a weakened immune system might have a very large number of mites, though, which can lead to particularly severe scabies. This is known as crusted scabies (Scabies crustosa) because it leads to a rash with thick areas of scaly and crusty skin.

People who have crusted scabies need more intensive treatment with both permethrin and ivermectin. This combined treatment with cream and tablets is then spread out over a longer period of about two weeks.

Treating crusted scabies isn't only more time-consuming; the affected people often feel more unwell than people with a normal case of scabies. Because of that, and the fact that it is more contagious, it is often treated in hospital. It is also easier to stop the disease from spreading in a hospital. Unlike with normal cases of scabies, the mites can be passed on through just brief contact with someone who has crusted scabies.