There is no single cause of eczema. It probably has a mixture of inherited and environmental causes that act together at different times.
You may be born with an increased likelihood of developing eczema, which you inherit from your parents.
When you are exposed to environmental factors, such as dust or pollen, this causes eczema to appear. There are several triggers that can make your symptoms worse.
Research suggests that atopic eczema is largely an inherited condition. This means that the cause lies in the genes that you inherit from your parents.
If a child's parents have atopic eczema, it is highly likely that the child will also develop the condition. Studies have shown that 60% of children who have a parent with atopic eczema will also have eczema. If both parents have atopic eczema, there is an 80% chance that a child will also have the condition.
It is not yet known exactly which genes are responsible for eczema.
If your genes make you more likely to develop atopic eczema, the condition will develop after you are exposed to certain environmental factors, such as allergens.
Allergens are substances that can cause the body to react abnormally. This is known as an allergic reaction. Some of the most common allergens that can cause atopic eczema include:
- house dust mites
- pet fur
Atopic eczema can sometimes be caused by food allergens, especially before the age of one. Foods that typically cause allergic reactions include:
- cows' milk
Some studies of children and young people with atopic eczema found that one-third to nearly two-thirds also had a food allergy. Having a food allergy increases the likelihood of your atopic eczema being severe.
Read more about food allergies.
Allergies do not always play a role. There are many other things likely to bring out eczema, including:
- cold weather
- harsh soaps
- washing too much
- rough clothing
Triggers can make atopic eczema worse, although they do not necessarily cause the condition.
Hormonal changes in women
Hormones are powerful chemicals that are produced by the body and have a wide range of effects. Changes in the levels of certain hormones can affect the symptoms of atopic eczema in some women.
Many women's eczema is worse at certain times during their menstrual cycle. Some women have a flare-up of their eczema in the days before their period.
The hormonal changes during pregnancy can also affect atopic eczema:
- more than half of all pregnant women find their symptoms get worse
- one-quarter of pregnant women find their symptoms improve
While stress is known to be associated with atopic eczema, it is not fully understood how it affects the condition. Some people with eczema have worse symptoms when they are stressed. For other people, their symptoms cause them to feel stressed.
Read more about ways to manage stress.
After vigorous exercise, sweating may make your eczema symptoms worse. Try to keep cool when you are exercising by drinking plenty of fluids and taking regular breaks.
Irritants can make your symptoms worse. What irritates you may be different to what irritates someone else with the condition, but could include:
- soaps and detergents, such as shampoo, washing-up liquid or bubble bath
- some types of clothing, especially wool and nylon
- very cold, dry weather
- unfamiliar pets
Other possible triggers include:
- substances that touch your skin, such as perfume-based products or latex (a type of naturally occurring rubber)
- environmental factors, such as tobacco smoke, living near a busy road or having water that contains lots of minerals (hard water)
- the changing seasons - most people with atopic eczema find that their symptoms improve during the summer and get worse in the winter