Ringworm - Causes 

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


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The 2 comments posted are personal views. Any information they give has not been checked and may not be accurate.

maria42 said on 04 November 2013

To Dan12345, you are misinterpreting the information. The 'at risk' group just lists factors which may make a person more likely to develop ringworm. It does not mean that you are in a risk group because you have ringworm. And it does not mean you must be in at least one of the risk groups.
Ringworm is a very common infection in people who have absolutely no other conditions.

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Dan12345 said on 24 September 2013

I am a 29 year old man who caught ringworm for the first time (first time I am aware of anyway!) on the inside of my thigh. Not sure, as you never really can be, of where I caught this from. I live in the countryside and do have two dogs. I have also engaged in what you would call high risk activities for HIV. After having a negative result, I would like to highlight that you can get ringworm at anytime in life and it does not mean you have HIV. HIV makes all infections more likely as you have weakened immunity, I do not think that the NHS should really list this here. It did make me think twice especially as I am not in any of the other at risk factors listed here e.g. not overweight (very slim!). I hope this helps anyone who may be panicking, ringworm is a symptom of ringworm and nothing else!

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