Brief overview
- Atopy – definition: genetic predisposition to allergy
- atopic diseases: e.g. allergic inflammation of the nasal mucosa and conjunctiva (as in hay fever or animal hair allergy), allergic asthma, neurodermatitis, food allergies, allergic hives
- Causes: Gene mutations that are hereditary
- Diagnosis: taking medical history, physical examination, allergy testing.
- Treatment of atopic diseases: Avoidance of triggers (if possible), medication against allergic symptoms, possibly specific immunotherapy as causative treatment
- Prevention of atopic diseases: Avoidance of smoking during pregnancy and breastfeeding, breastfeeding, possibly special baby food (benefit controversial), no exaggerated hygiene etc.
What does atopy mean?
Atopics are genetically susceptible to reacting allergically to contact with actually harmless substances from the environment (e.g. the protein of certain pollens). Their immune system forms IgE (immunoglobulin E) type antibodies against them, and those affected develop typical allergic symptoms.
When immune cells with IgE antibodies capture allergy triggers (allergens) on their surface, they release pro-inflammatory messenger substances such as histamine in response. These then trigger allergic rhinitis and other allergy symptoms.
What are the atopic diseases?
Atopic diseases can develop on the basis of atopy due to various environmental factors. They are also summarized under the term “atopic circle of forms”. Typical examples are:
- allergic bronchial asthma: contact with an allergen (such as pollen, house dust) triggers an asthma attack. In addition to allergic asthma, there is also non-allergic asthma, in which physical exertion or cold, for example, trigger the attacks.
- Neurodermatitis (atopic eczema, atopic dermatitis): This inflammatory skin disease usually appears in early childhood. It is characterized by chronically recurring, intensely itchy skin eczema.
- allergic hives (urticaria): contact with an allergen triggers intensely itchy wheals and/or tissue swelling (angioedema = Quincke’s edema).
Difference between atopic and allergic diseases
Atopic diseases are allergic diseases in which antibodies of the immunoglobulin E type are significantly involved.
For example, in allergic contact dermatitis (such as nickel allergy) and drug exanthema, the allergic symptoms are mediated by T lymphocytes (a subgroup of leukocytes) and occur 12 to 72 hours after allergen contact. Physicians refer to this as a type 4 allergic reaction (late type).
Learn more about the different allergic reaction types here.
What are the causes of atopy?
Researchers have also been able to identify a number of sites (gene loci) on various genes which, when altered (mutated), increase the risk of hay fever, allergic asthma & Co. However, the majority is still unclear.
Atopy is hereditary
What is clear, however, is that the genetic predisposition to atopic reactions is hereditary.
- This risk increases to 40 to 60 percent if both parents suffer from an atopic disease.
- If both mother and father suffer from the same atopic disease, the risk for the child increases to 60 to 80 percent.
By comparison, children whose parents do not have an atopic disease have a risk of up to 15 percent of developing such a disease themselves.
What symptoms indicate atopy?
There are some skin symptoms that can indicate atopy. These so-called atopy stigmata include, for example:
- Hertoghe’s sign: The lateral part of the eyebrow is partially or completely missing. Usually both eyebrows are affected.
- Ichthyosis hand, foot: increased drawing of the skin lines of the palm and soles of the feet
- double lower eyelid wrinkle (Dennie-Morgan wrinkle)
- dry, brittle, cracked, scaly skin (xerosis cutis)
- pale, gray-white facial color and dark circles around the eyes (dark skin coloration = haloing around the eyes)
- fur cap-like hairline
- white dermographism: if one strokes the skin with a spatula or fingernail, for example, this leaves a whitish trace.
These stigmata are an indication but not a proof of atopy! They can also have other causes.
How can an atopy or atopic disease be diagnosed?
During the physical examination, the physician looks for stigmata that may indicate atopy (see: Symptoms).
Suspicious triggers of allergic symptoms can be unmasked in allergy tests. These are often skin tests such as the prick test:
Blood tests can also provide clarity in the case of a suspected atopy or atopic disease. If, for example, the total level of immunoglobulin E is elevated, this indicates an allergic disease. However, the elevated measured value can also have other reasons. In addition, an allergy can also be present with normal total IgE.
You can read more about the various test procedures for suspected allergy in the article Allergy test.
How is atopy treated?
There is nothing that can be done about the genetic predisposition itself. However, if an atopic disease has already developed, those affected should avoid the trigger as far as possible.
Allergic symptoms can be controlled with various medications (as tablets, nasal spray, etc.):
- Antihistamines weaken or block the effect of histamine – the messenger substance that plays a major role in the development of allergy symptoms.
- Corticosteroids (“cortisone”) have an anti-inflammatory effect. They are used, for example, in asthma and severe hay fever.
- Mast cell stabilizers inhibit the release of histamine from the so-called mast cells. They thus act primarily as a preventive against allergic symptoms.
All the drugs mentioned are directed against the symptoms of an atopic or allergic disease. With specific immunotherapy (hyposensitization), on the other hand, doctors try to get to the root of the allergy:
Allergen-specific immunotherapy is well suited for the treatment of allergic rhinitis (with or without allergic conjunctivitis), i.e. hay fever, for example. Its efficacy is also well established in allergic asthma and insect venom allergy.
This is what prevention of atopy looks like
Atopy itself cannot be prevented. However, there are a number of things that can be done to prevent an atopic disease such as hay fever or allergic asthma from actually developing on the basis of a genetic predisposition.
To this end, pregnant and breastfeeding women should not smoke. This lowers their child’s risk of allergies. For the same reason, (expectant) mothers should avoid secondhand smoke as much as possible.
Special infant nutrition (HA nutrition) is often used for children with an increased risk of allergies who are not (or cannot) be breastfed sufficiently. However, the benefit of this special food is not proven.
What has been proven to be effective in preventing allergies is avoiding too much hygiene in infancy.
You can read more about this and other ways to prevent atopic or allergic diseases in the article Allergy prevention.