The scabies mite life cycle

Scabies is a skin condition that is caused by the human parasite Sarcoptes scabiei. An infestation (the presence of animal parasites inside the body) starts when a female mite burrows into your skin.

Male mites move between different burrow sites looking to mate with an unfertilised female. After mating has taken place, the male mite dies and the female begins to lay eggs. The eggs hatch around three or four days later.

After the eggs have hatched, the young mites move to the surface of the skin where they mature into adults. It takes between 10 to 15 days for the mites to mature. The male mites stay on the surface of the skin, and the female mites burrow back into the skin in order to create a new burrow. The life cycle is then repeated.

Without effective treatment, the life cycle of the scabies mite can continue indefinitely. Scabies mites are resistant to soap and hot water and they cannot be scrubbed out of the skin.

The exact cause of the intense itchiness that is associated with scabies is unknown, but most experts believe that the it is caused by the immune system reacting to the mites and their saliva, eggs and faeces (stools).

How scabies is transmitted

Scabies mites cannot fly or jump, so they can only move from one human body to another if two people have direct and prolonged physical contact. For example, scabies mites can be transmitted by:

• holding hands with someone who is infected for a prolonged period of time
• having sex with someone who is infected
• sharing a bed, towels or clothes (although this is rare)

Transmission through brief and limited physical contact, such as shaking hands or hugging someone, is unlikely.

Scabies mites can survive outside the human body for between 24 to 36 hours, so it is possible to become infected by coming into contact with contaminated clothes or bed linen. However, this is a far less common way of acquiring the condition.

Scabies infestations can spread quickly because people are usually unaware that they have the condition until two to three weeks after the initial infection has occurred. There is an increased risk of catching scabies in confined environments, such as schools and nursing homes, where people are in close proximity to one another.

People often regard scabies as a condition that is caused by poor personal hygiene and living conditions. However, there is no evidence to suggest that this is the case. Scabies can affect people from all walks of life, although certain groups have an increased risk of getting the condition.

Risk groups

Some groups of people have an increased risk of catching scabies because they are in close contact with lots of other people. Those with an increase risk include:

• children – this is due to the outbreaks of scabies that can occur at schools and nurseries
• young mothers – who are in close contact with affected children
• elderly people who live in nursing homes
• people who are sexually active