BMJ Group Medical Reference
You can get malathion lotion on prescription or buy it over the counter. But it's best to see your doctor or nurse to check that the problem is scabies before starting treatment. The brand names for malathion lotion are Derbac-M and Quellada M.
Malathion tends to be the second choice of treatment for scabies, after permethrin. It can be used for people who can't use permethrin, or if permethrin hasn't worked. 
You need to cover your whole body, including your neck, face, scalp, and ears with the lotion.  You keep it on for 24 hours and then wash it off. During those 24 hours, if you wash any part of your body with soap, such as your hands, you need to treat that area again with malathion. You need to repeat the process after seven days.
There hasn't been any really good research on malathion as a treatment for scabies. But some lower-quality studies found that it got rid of scabies for up to 8 in 10 people within four weeks of treatment. 
The main side effect for malathion is a burning feeling on your skin. 
For references related to Scabies click here