Are allergies cause of atopic eczema?

There has been a widespread belief that atopic eczema is caused by allergy; that as long as one stays away from the source of allergy, eczema would disappear. However, this is not true.

Atopic eczema, asthma, hay fever and food allergies constitute different facets of the same genetic predisposition in atopy. In other words, if you have one of the atopic diseases, you are more susceptible to have one or more of the others.

Thankfully, most never have more than one. In some patients, atopy may even disappear completely. It is not infrequent for different atopic diseases to ensue different clinical courses. For example, eczema can get better while asthma can get worse.

Although allergy is not the cause of eczema, allergens do trigger flare ups. In other words: If you have not been in contact with the allergens, exacerbations are less likely.

This is best illustrated with the example of asthma and eczema. While asthma can be triggered and worsened by allergens, non-allergens such as cold temperature and psychological stress could also precipitate exacerbations.

As for eczema, while it can be triggered and worsened by allergic factors, non-allergic factors are especially those of importance. These include climatic and psychological conditions, heat / sweat, mechanical and chemical irritation of the skin, such as scratching and irritation of textiles, excessive use of soap and water, perfumed soap and tobacco smoke. Infections are a frequent cause of eczema exacerbations.

Allergens can be acquired via three routes

• Direct skin contact
• Inhalation
• Ingestion

An allergen is a  substance  that may cause allergic reactions. A kind of food may contain several allergens and is then referred to as “allergen source” Allergens can come in contact directly with skin, clothing or air.

Those who are allergic to cat dander, when in direct skin contact with cats (e.g. Cuddling), can trigger skin inflammation at the site of contact within minutes, such as redness, itching and perhaps swelling. During the next few days, the typical symptoms of eczema will develop.

Perfumes, which spreads through the air – though not always in direct contact – can also cause the same symptoms.

Allergens from animals’ body, house dust mites and skin microflora are also described as causes of flare-ups in eczema.

Food substances can cause flare-ups of eczema in both allergic and non-allergic reaction patterns. In the latter case an allergy test will obviously not turn out to be positive.

There are some food that contain substances which in itself is itch-provoking (usually not allergens like- cf. jellyfish and nettles). Examples are citrus fruits – orange, mandarin, lemon, grapefruit and juice of these fruits. Likewise, tomatoes and its products, strawberry, chocolate, deep-water fish, goat cheese, heavily fried and smoked food are also some other examples.

There are quite a few kind of food that cause the majority of eczema outbreaks on the basis of allergy. Among young children, they are cow’s milk, eggs, soy and peanuts. In older children and adults, wheat, nuts, fish and shellfish are more common.

Allergens from food may pass into breast milk and cause allergies in genetically susceptible children. For example, mother taking (most often) cow’s milk or eggs can exacerbate eczema in breastfeeding children. Most kids can tolerate cow’s milk at the age of two. By school age, allergy to eggs, soy and wheat usually disappear.

If allergy only plays a role for some patients with atopic eczema, then who should be evaluated for allergies?

The youngest children who present with major ailments from eczema warrant detailed assessment by specialists. As for older children and adults, besides those who are severely affected, patients who do not experience marked deterioration from allergen contact rarely require investigations for allergens.