Allergy Basics
NATIONAL JOURNAL OF HOMOEOPATHY 2004 Nov / Dec VOL VI NO 6.
Dr C H Asrani

What is Allergy?
Allergy reflects an overreaction of the immune system to a normally harmless substance. These substances, be they food, pollen, a bee sting, dust mites, or a host of others, are called allergens. They can trigger sneezing, wheezing, coughing and itching. Allergic reactions range from mildly irritating to moderately bothersome to severely incapacitating and may even prove fatal. Allergies are the 6th leading cause of chronic disease globally.

Mechanism of Allergy
A properly functioning immune system is a well-trained and disciplined protective mechanism for the body. Our immune system is able to identify and destroy foreign invaders as well as identify cells infected internally with bacteria, viruses, parasites and any other foreign protein substance. As soon as a foreign protein enters the body, the lymphocytes identify the protein, kind of fingerprint it and determine if it belongs to the host or not. Whenever they discover a cell that seems threatening, they immediately begin countermeasures.

After a B-lymphocyte identifies a particle or cell as a foreign protein (antigen) it changes itself into a plasma cell. This plasma cell produces immunoglobulins (Ig), specifically engineered to fight and destroy that specific protein that the lymphocyte identified in the first place. Of the different immunoglobulins (IgA, IgD, IgE, IgG & IgM), IgE is the class that forms an allergic reaction. They attach to other white blood cells in what is called the sensitizing exposure.

Now, when the protein enters the body again, at least 7-10 days after the sensitizing reaction, the IgE primed mast cells release many chemicals including histamine that try to destroy the "invading" protein. Histamine lowers the local blood pressure and causes itching and swelling. It can also cause wheezing, an itchy, runny nose, nausea, vomiting or diarrhea. (This is basis of modern medicine wherein "anti- histamine" drugs are used to treat allergies).

As versatile as the immune system is, it sometimes makes mistakes. Allergies are the result of a hypersensitive immune system. In the body of an allergic person, the immune system misidentifies an otherwise innocuous substance as harmful and attacks it with ferocity far greater than required - the same reaction that normally help protect us from infectious diseases.

Common Allergens
As the cover illustrates, everything under the sun including the sun can give allergic reaction. Grasses, moulds, dust along with some common food items such as milk, eggs, shell-fish and wheat form some of the common allergens and sinusitis, allergic rhinitis, urticarial, contact dermatitis and reactions to food and insect stings are the most common allergy types.

Why different people respond differently to, so called, Allergens?
The capacity to become allergic is an inherited characteristic. Yet, although one may be born with the genetic capability to become allergic, allergies to specific allergens does not begin automatically. Several factors must be present for allergic sensitivity to develop:

• The specific gene acquired from parents.
• Exposure to one or more allergens to which one already has a genetically programmed response.
• The degree and length of exposure

Urticaria (Hives)
Urticaria is one of the commonest manifestations of skin allergy, appearing as edematous pink or red wheals of variable shapes and sizes. It is very common with almost 10-20% of the population having at least one episode in their lifetime. Most episodes of urticaria disappear quickly in a few days to a few weeks. Occasionally, a person will continue to have hives for many years. Lesions disappear without leaving any mark/ sign behind.

Pathophysiology

Allergic reaction

Histamine release from "mast cells" along the blood vessels in the skin

Plasma leaking out of capillaries

Urticaria

Symptoms and signs

• The skin lesions are often pink or pale hives. There may be erythema in the surrounding skin.
• There may be considerable itching but telltale signs of scratching are rare.
• The size of the lesions varies from 1 mm to large confluent hives.
• The hives often cover large areas of the skin.
• Individual lesions disappear within 24 hours, but new lesions may develop continuously.

Acute urticaria (duration < 6 weeks)

• Most acute urticarias are associated with infections, although the aetiological connection remains unproven. The drugs used for the infection are often blamed although they are usually not the causative factor. Common cold is commonly associated with urticaria.
• The most common foods that cause hives are nuts, chocolate, fish, tomatoes, eggs, and milk. Fresh foods cause hives more often than cooked foods. Food additives eg colours and preservatives may also cause hives.
• In acute cases, cause can generally be identified.

Recurrent acute urticaria

• Recurrent urticaria's occur at intervals of years or months during infections or irrespective of them. Finding the cause is exceptional and investigations are usually not helpful.
• Acute attacks of urticaria and anaphylaxis may sometimes be caused by the combined effect of cereal or other food allergy and exercise.
• Urticaria may also be caused by contact with, eg animal saliva or latex. Investigations
• No investigations are necessary in acute urticaria.

Chronic urticaria (Continuously or intermittently for at least 6 weeks)

• Chronic urticaria is sometimes associated with infections, allergies, drugs or other diseases and the causative agent is more difficult to identify.
• Identify infection foci, allergies etc depending on the case
• Remove/manage the causing factor

Idiopathic chronic urticaria

• The symptoms are often daily.
• The treatment is general as no clear cause is found.

Dermatographism (urticaria factitia)

• A (viral) infection is often a triggering factor.
• The duration of the disease is usually < 1 year in young people, 2-4 years in middle-aged people.

Perspiration urticaria

• In young adults severely itching hives 1-2 in diameter are triggered by perspiration (and excitement).
• The duration of the symptom is < 2 hours at a time.
• The diagnosis is made with "a staircase test": any exercise resulting in perspiration.

Treatment
The best treatment is to find and remove the cause. This is not an easy task and often not possible. The treatment hence is empirical and usually prescribed to provide symptomatic relief.

Allergic Dermatitis
It is an itchy skin condition caused by an allergic reaction to some material in contact with the skin, causing itching, redness and blisters. It usually results from an exposure lasting for weeks or months. The most common causative agents are nickel, rubbers and glues, chrome and cobalt, perfumes and other compounds used in skin and hair care products. It may settle down over some days providing the skin is no longer in contact with the allergic material.

Less commonly it may also be an immediate allergic reaction. The causative agents, then, include latex, bovine hair and vegetables.

Symptoms

• The symptoms initially occur at the site of contact but they may spread to other areas.
• The symptoms recur within 1-2 days from the onset of a new exposure and cease gradually after the exposure has stopped.

Diagnostics
Allergic dermatitis should be suspected on the basis of the location.

Typical sites for allergic dermatitis include

• Face and neck (cosmetics & jewelry)
• Armpits (clothes, deodorants)
• Wrists and hands (metals, leather, tools, chemicals)
• Waist (latex, metals)
• Buttocks (haemorrhoid ointments and suppositories)
• Thighs and legs (socks, rubber boots, topical treatments for leg ulcers)
• Feet (metals, gum, leather, dyes, contact glue, chromium, antimycotics)

Treatment is always directed at eliminating the sensitizing agent in addition to the remedies. Patients with history of allergic dermatitis have to, proactively, look for products that do not cause reactions. With such a high incidence of allergies, hypoallergenic products are available in most segments.

Allergic Rhinitis
Rhinitis is the inflammation of the nasal membranes and is characterized by sneezing, nasal congestion, nasal itching and rhinorrhoea, either alone or in combination. The eyes, ears, sinuses and throat can also be involved. Allergic rhinitis is the most common cause of rhinitis. It is an extremely common condition, affecting approximately 20% of the population. Systemic effects, including fatigue, drowsiness, and malaise can occur from the inflammatory response. These symptoms often contribute to impaired quality of life.

Pathophysiology
It involves inflammation of the mucous membranes of the nose, eyes, eustachian tubes, middle ear, sinuses and rarely pharynx. The nose invariably is involved and the other organs are affected in certain individuals. Inflammation of the mucous membranes is triggered by an immunoglobulin E (IgE)-mediated response to an extrinsic protein (allergen).

Trigger factors
Identifying trigger factors constitute an important part of history taking and examination. The treating physician must determine whether symptoms are related temporally to specific trigger factors. This might include exposure to pollens, mites, mold spores, specific animals or dust while cleaning the house.

Irritant triggers such as smoke, pollution and strong smells can aggravate symptoms in a patient with allergic rhinitis. Most patients describe year-round symptoms that do not appear to be associated with specific triggers. This could be consistent with non-allergic rhinitis, but perennial allergens, such as dust mite or animal exposure should also be considered in this situation. With chronic exposure and chronic symptoms, the patient may not be able to associate symptoms with a particular trigger.

Management

• Careful removal of allergens (pets, house dust) is the basic action in all forms of allergic rhinitis.
• Identification and treatment other causes of rhinitis and aggravating factors (polyps, deviated nasal septum, adenoids in children etc).
• Instructions to patients with allergic rhinitis on how to minimize exposure to allergens.
• Identification of non-specific irritants in the patient's environment (smoking, dusts, fumes)

ARIA guidelines
ARIA (Allergic Rhinitis and its Impact on Asthma) guidelines, which have been drafted by an expert panel together with WHO, are research and treatment guidelines for general practitioners and specialists (www.whiar.com). The emphasis is on the concept "one airway, one disease". The main message of the working group is that the connection and inter-relatedness of rhinitis and asthma symptoms must be kept in mind and that examinations and treatment should be combined, when possible. The ARIA classification of rhinitis has been defined on the basis of the duration of the symptoms and their impact on quality of life. A must read for us all!

With proper management and patient education, allergic diseases can be controlled, and people with allergies can lead normal and productive lives. This widens the scope of our responsibility patient education to the forte.

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