Ringworm is a skin infection caused by a fungus.
Ringworm is caused by a particular type of fungi, called dermatophytes, which live off keratin. Keratin is a tough, waterproof tissue found in many parts of your body including your skin, nails and hair.
This explains why ringworm infections mostly affect your skin, nails or scalp.
How ringworm spreads
The fungi are tiny spores that are tough enough to survive for months on your skin, in soil or on household objects such as combs or towels.
The fungi 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're a carrier of a ringworm infection, you can unknowingly pass the condition onto children, who may then go on to develop symptoms.
Who's at risk?
You're more likely to develop ringworm if you:
- are very young or old
- are African-Caribbean (in the case of scalp ringworm)
- have type-1 diabetes
- are very overweight
- have a medical condition that weakens your immune system, such as HIV or AIDS
- are on 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)
