Certain things can trigger eczema or make it worse.Allergens
Some people who have eczema get worse symptoms when they're in contact with certain things. Their skin gets itchy and inflamed. Things that cause these symptoms are called allergens, and the skin trouble they cause is an allergic reaction.
Here are some of the common allergens:  
House dust mites (their droppings)
Animal skin, feathers, or fur
Certain foods, only for some people.
Some things can make your eczema worse. They are called irritants. Over time, you'll learn which things cause problems for you or your child. Common irritants are: 
Certain fabrics, such as woollen or synthetic fabrics
Cosmetics or perfumes
Detergents (washing powder or liquids, fabric softener)
Even water can be an irritant, if you get your skin wet a lot (for example, if your job involves washing things). If your hands are often wet and you don't use a moisturiser after drying them, the skin could become dry and itchy. Then the 'itch-scratch' cycle could start. For more information, see What is eczema?
There isn't any strong scientific evidence that avoiding these irritants will make your own or your child's eczema get better. But many people find that avoiding these irritants helps their eczema.Stress
Stress doesn't cause eczema, but stress, anger and frustration can make symptoms worse. If you've just moved to a new area or your child is having problems at school, you may notice the eczema getting worse. In adults, starting a new job or coping with the death of someone close can trigger eczema.  
To learn more, see What will happen to me?
If you have an allergy to something, your body overreacts when you come into contact with it. The thing you are allergic to is called an allergen. Most allergens are harmless to most people. But if you're allergic to something, your body's system for fighting infection (your immune system) is too sensitive to that allergen. It triggers changes that are called allergic reactions. For example, pollen is an allergen for some people. If you're allergic to pollen, you'll sneeze and have runny eyes when pollen is in the air.
You have an allergic reaction when your immune system overreacts to a substance that is normally harmless. You can be allergic to particles in the air you are breathing, like pollen (which causes hay fever) or to chemicals on your skin, like detergents (which can cause a rash). People can also have an allergic reaction to drugs, like penicillin.
Inflammation is when your skin or some other part of your body becomes red, swollen, hot, and sore. Inflammation happens because your body is trying to protect you from germs, from something that's in your body and could harm you (like a splinter) or from things that cause allergies (these things are called allergens). Inflammation is one of the ways in which your body heals an infection or an injury.
For more terms related to Eczema
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