The itching and rash that result are a kind of allergic reaction. If a person has never been exposed to scabies mites in the past, he or she is not likely to show symptoms for a considerably longer amount of time than a person who has been exposed in the past. A person who is infected for the first time may take as long as four to six weeks after originally being infested to begin to show these symptoms. In contrast, a person with prior exposure is likely to begin to show symptoms in a few days.

The question of what causes scabies is also answered by the question of where scabies comes from. The disease is contagious and is most often spread by either prolonged contact with the skin, which is a fertile breeding ground, or through skin to skin contact. In some situations, it may be spread as any number of sexually transmitted diseases. 

It almost always is spread through an extended amount of skin to skin contact between a person who does not have the mite and someone else who already does. In most situations, the mites will prefer to start burrowing into the body wherever the point of contact is made. As a result, when skin to skin contact occurs during sexual intercourse, the groin area is likely to be infested. 

However, it is necessary to remember that scabies is not always transferred as a sexually transmitted disease. Rather, it is more than possible to acquire scabies through casual physical contact. There are also less common situations where a person can contract an infestation of scabies through sharing his or her clothes or bedding with someone else. It is also theoretically possible to contract scabies through touching an object that contains mites, but this is more rare than any of the aforementioned modes of contact.

When searching for the cause of scabies, it is important to be aware that severe and continuous itching at night may be a sign of scabies infestation in a person. This is also likely to be the case if the infestation appears to affect multiple members of the household. Keep in mind that the bites of scabies are likely to be small and resemble those of an insect or pimples. Keeping this information handy will increase one's chances of discovering what causes scabies.