Allergy or allergic diseases – what these terms mean

Allergies are acquired over time, mainly through repeated contact with allergens and additional environmental factors, writes PROFESSOR JAMILA ABOOBAKER.

BY ‘allergy’ we mean a hypersensitive reaction of the body to foreign matter in the environment: nearly always proteins from pollens, house dust-mites, animal hair (danders). These foods and drugs are called allergens, which we encounter by eating, breathing or simply contact with the skin. The body reacts with an ‘excessive’ defence reaction. This excessive reaction leads to various allergic symptoms. The immune system is always involved. We know of over 20 000 allergy triggering substances.

Causes or aetiology

A child is never born with an allergy. Allergies are acquired over time, mainly through repeated contact with allergens and additional environmental factors. Some subjects have an innate tendency to develop a hypersensitivity reaction, subsequently proven to be allergic, which we refer to as an atopic predisposition; atopies are hypersensitivity reactions which are promoted by a familial predisposition.

Atopic subjects react to certain antigens (known as allergens) by producing large quantities of specific IgE immunoglobulins. These bind to the so-called mast cells, thus sensitising them.

The next time such a person comes into contact with the allergy-provoking allergens, mast cell bound IgE antibodies are activated. This leads to the release of mediators, like histamine from granules. Such mediators cause multiple symptoms of an ‘atopic disease’ innate, and environmental factors cause these allergies.

Classification:

• Allergies are classified according to organ involvement- nose, eyes and skin
• According to symptoms: urticarial, eczema, asthma
• According to pathogenic mechanisms: ‘Gell and Coombs’ classification
• According to allergen – food allergy, animal protein, chemical e.g. nickel
• According to clinical course – acute/ chronic e.g. life threatening anaphylaxis
• According to genetic parameter – familial
• According to age – childhood, adult

Type I – IgE mediated: hayfever, asthma, urticaria (hives), atopic eczema

These are mediated by IgE on mast cells

Type II – cytotox: red cell deficiency (haemolytic anaemia)

platelet deficiency (thrombocytopenia)

white cell deficiancy -( agranulorcytosis leads to frequent infection)

Type III – immune complex diseases due to complications lead to drug reaction

Type IV- allergic (delayed hypersensitivity that leads to contact dermatitis)

Clinical features of atopic diseases are:

1. Allergic bronchial asthma: There is frequent coughing with breathing difficulties, which leads to wheezing.
2. Allergic rhinitis (hay fever): These are seasonal or year round reactions to pollen, domestic pet hairs (dander) or house dust mites. They get frequent colds and runny nose with sneezing, with no infection.
3. Atopic dermatitis (atopic eczema): Itchy, red cutaneous eruptions. In infants, the eruptions are on the cheek, forehead, chest and arms. In older children, the rash becomes more localised to the elbow and knee folds.
4. Food allergies – is intolerance to certain foods, which manifests as stomach aches, flatulence without viral or bacterial infections. This is not lactose intolerance.

Allergic rhinitis: This presents as colds and runny nose and have nasal stuffiness, sneezing, itching and swollen eyelids all year round or seasonally when the pollen count is high. The mucosa swells, increased viscous secretion builds up in the sinuses, resulting in facial discomfort and headaches.

Also, the target organ showing the first signs of an allergic disease. This is an itchy, red cutaneous eruption, as mentioned, on the face of infants, the forehead, chest and cheeks; and as the child grows up it goes to the knee folds; the wrists and calves are also affected.

Not all allergies are atopic diseases. Tobacco smoke promotes allergic reactions and this is a hereditary predisposition for allergies; it is not an infection; it is the tobacco smoke that provokes it.

50 per cent of allergies are inherited and 50 per cent are due to environmental factors.

Allergy risk can be predicted – 20 to 30 per cent of all children from both allergic parents can develop allergies.

Special investigations

To determine the risk factor for allergy, one has to do –

1. Immunoglobulins (IgE) level

The total immunoglobulins are raised sky high in most of these patients. If neither parent is allergic then there is five to 15 per cent tendency. If one parent is allergic, then 20 to 40 per cent will develop allergies. If a sibling is allergic then 25 to 30 per cent are affected, if both parents are allergic then 40 to 60 per cent or even 80 per cent become allergic, and this can be done as soon as possible. We can work out the percentage in patients.

The first manifestation of an allergy can be prevented, diminished or delayed, if we do the IgE levels.

2. We also do the FX5 food levels, and tell the mothers to avoid certain things in the child’s diet.

In her diet during pregnancy she must avoid allergy causing food. She must not smoke and when the baby is born, she must exclusively breastfeed. This is the most important advice that we can give to mothers of allergy-prone children.

3. Breastfeeding for at least six months is essential. There are formulas which can be given e.g. Nan HA, where the milk protein is hydrolysed.

There must be no smoking in the house; if dad smokes then he must do so outside.

4. Animals and pets must be avoided completely.
5. The house dust mites which cause allergy can grow in carpets, upholstery, blankets, duvets and mildew in the bathroom; and damp rooms must be avoided.
6. Pollen, like grass and especially hazelnut blossoms must be avoided.
7. Patients must avoid ear-piercing with nickel as this can lead to nickel allergy. Nickel contact dermatitis can develop in many patients with allergy.

Management

• Diet during pregnancy: avoid nuts and certain foods.
• A list of foods that a patient has to avoid (fish, eggs, wheat, gluten, citrus fruits, peanuts, hazelnuts, celery, shellfish and soya products).
• The child must eat fresh fruits, vegetables.
• Swiss Parquet or linoleum floors instead of carpets. This is to protect exposure to house dust mites.
• Mattress covers can be boiled and dried in the sun and this will reduce house dust mite in the bedroom. We get good sunshine in South Africa so there is no problem.
• Leather upholstery is advisable instead of fabric upholstery.
• Fluffy toys are a big ‘no’ for these children.
• Proper ventilation is very important to prevent mildew in rooms, and household pets as mentioned are contraindicated for children, and these are all taught to the mother by the midwives.
• The mother should get extra calcium as she needs to give the baby calcium from her milk.
• Fresh food and vegetables also contain a lot of vitamins that the mother and child needs.
• If the baby suffers from bloating and gas then one puts the child over the shoulder and taps the back so that the baby burps after a feed.
• If they develop a rash that is stubborn then one can do a patch test: here one can start with ‘prick tests’ that the child is allergic to.
• Fragrance must be avoided in the cosmetics. We use hypoallergenic products
• Avoid scented soap.

Professor Jamila Aboobaker [MB ChB (UKZN), FF Derm (SA), College of Medicine of South Africa(CMSA), FRCP (London), PhD (UKZN)] is a senior dermatologist at Dermatology Skin Care & Laser Specialists, honorary tutor and examiner at UKZN and examiner at The Colleges of Medicine of South Africa (CMSA).