Clive Anderson - AT THE DERMATOLOGISTALLERGIES ARE very common problems. It is estimated that two out every 10 persons have an allergy. Allergies occur as a result of an overactive immune system.
The body's immune system is an amazing defence mechanism. The immune system patrols the body identifying and neutralising invaders such as bacteria and viruses as well as tumour cells. This keeps the body healthy. This fantastic biological warfare unit sometimes makes a mistake however and identifies a harmless substance as a threat to the body and attacks it with great ferocity.
The main soldier of the immune system is the white blood cell or lymphocyte. These cells patrol the body looking for trouble. When they encounter a foreign agent (virus, bacteria) they take its picture and go off to produce antibodies specifically to fight against the foreign agent. Because the foreign agent triggers antibody production it is called an antigen.
In a properly functioning immune system the lymphocytes are able to differentiate between harmless proteins and the ones that are a threat to our bodies. The hyperactive immune system does not and as a result identifies the shellfish that we have eaten as an invader and mounts a defence. Large numbers of antibodies are produced. These antibodies attach themselves to certain cells called mast cells. The body is now primed; it is sensitised to the allergen. This process of sensitisation, after the first exposure may last a week or 10 days.
The next time the offending protein or allergen gets into the body, it triggers a destructive cascade of events. The antibodies, which are attached to the mast cells, recognise and bind to the invader. This binding alerts certain special proteins in the body to attack thus destroying the invader and along with it the attached mast cell. The destruction of the mast cells causes the release of histamine and other chemicals into the tissues and blood. Symptoms arise based on the part of the body affected by this cascade of events.
SYMPTOMS
Some common symptoms are itching - skin, nose, eyes; wheezing; sneezing; wheals (urticaria); diarrhoea, vomiting. In a mild allergic attack the symptoms listed above affect a specific part of the body. In a moderately severe attack symptoms spread to other parts of the body. These may include itching and wheezing.
A severe allergic reaction is called anaphlaxis. It is a rare, life-threatening emergency affecting the whole body. More serious symptoms such as swelling to the mouth and throat may affect breathing and swallowing. A rapid fall in blood pressure can cause dizziness and loss of consciousness.
Most allergies are inherited, meaning they are passed on to children through their genes. Persons inherit a tendency to be allergic, not a specific allergy such as shellfish allergy. When one parent is allergic the child has a 50 per cent chance of developing an allergy. This risk jumps to 74 per cent if both parents have allergies.
The commonest allergens are foods like shellfish and nuts, or seasonal allergies caused by pollen, house dust or mold. Medicines such as some antibiotics, penicillin most commonly may be the cause or insect venom. Treatment involves avoiding the allergen if possible. For example, not eating crab, shrimp or lobster in a shellfish allergy. This is not possible if the allergen is all around such as pollen. Medicines such as antihistamines, decongestants, corticosteroids work to reduce the symptoms. In immunotherapy a series of injections of the allergen, starting with a very low dilution, is administered. These work to reduce the body's production of antibodies.
Dr. Clive Anderson is a Dermatologist and Venereologist.
