Causes of ringworm 

Ringworm is a skin infection caused by a fungus.

Ringworm is caused by fungi called dermatophytes, which live off keratin. Keratin is a tough, waterproof tissue found in many parts of the body, including the skin, nails and hair.

This is why ringworm infections mostly affect the skin, nails or scalp.

How ringworm spreads

The fungi are tiny spores tough enough to survive for months on your skin, in soil or on household objects, such as combs or towels. The spores can be spread in four different ways:

  • human-to-human contact
  • human-to-animal contact  for example, by stroking an infected dog or cat
  • human-to-object contact  both animals and humans can leave traces of fungi spores on objects and surfaces, such as towels, clothing, bed linen, combs or brushes
  • human-to-soil contact  less commonly, you can develop a ringworm infection after lengthy exposure to infected soil

As an adult, you can become a carrier of scalp ringworm without developing any symptoms. This is because your body has usually developed a defence against the infection by the time you reach adulthood.

If you are a carrier of a ringworm infection, you can unknowingly pass the condition onto children, who may then go on to develop symptoms.

Risk groups

You are more likely to develop ringworm if you:

  • are very young or very old
  • are African-Caribbean (in the case of scalp ringworm)
  • have type 1 diabetes
  • are very overweight (obese)
  • have a medical condition that weakens your immune system, such as HIV or AIDS
  • are receiving medical treatment that weakens your immune system, such as chemotherapy or steroid tablets
  • have had fungal infections in the past
  • have hardening of your arteries (atherosclerosis)
  • have poor circulation (specifically a condition called venous insufficiency, where the veins in your legs have trouble moving blood back to your heart)

Page last reviewed: 14/03/2013

Next review due: 14/03/2015