Allergies are extremely commonplace, with over 44% of adults in the UK suffering from them at some point in their lives. But we still don't know exactly why we develop them. Alarmingly, the number of allergy sufferers is growing with every year.
Children are particularly susceptible to allergies. However, these can often disappear as they get older. By the same token, people can sometimes develop allergies in later life that they never had before. The actual triggers are hard to decipher, although pre-existing hereditary conditions and environmental factors seem to make a vital contribution.
An allergy is defined as a condition whereby a particular substance triggers an involuntary reaction in the body. This reaction typically involves the immune system and is unrelated to the normal effects of the substance in question. For these reasons, an allergy should not be confused with a sensitivity or an intolerance.
If a person has a sensitivity to a substance, this generally means that they feel that substance's normal effect more intensely than other people. For instance, a person with a sensitivity to alcohol may become intoxicated more easily than is normal. An intolerance is when a substance causes a negative effect that is unrelated to the immune system and may depend on the quantity of the substance present. So a food intolerance may cause sickness or digestive problems if more than a small amount of the food in question is eaten, whereas an allergic reaction normally takes place instantly regardless of quantity, and affects numerous organs besides the stomach.
Many people suffer from food allergies, particularly to dairy products, types of nuts, and shellfish. Hay fever is also a type of allergy, one that is triggered by grass and hair pollen. People can also be allergic to minute substances in the air around them, particularly indoors. These substances include dust mites, animal dander (particles of skin and hair, often from pets) and mould. Others also suffer severe allergic reactions to insect bites or stings, or to antibiotics or other medicines. Latex and chemicals found in common household products can also be causes of allergies.
Most allergies are fairly mild and — while the symptoms are annoying — they are rarely life-threatening. These can include sneezing and a runny nose; itchy and/or watery eyes; wheezing and coughing; a skin rash and/or swelling; asthma and eczema. A more severe reaction could cause the sufferer to experience anaphylactic shock — a medical emergency requiring immediate treatment.
Anaphylactic shock, or anaphylaxis, is a severe over-reaction of the immune system to the presence of a substance. Severe swelling, shortness of breath, vomiting and low blood pressure causing lightheadedness and collapse are typical symptoms. The swelling itself can have serious consequences. For instance, swelling closing the eyes so the sufferer cannot see, or closing the throat so that the sufferer cannot breathe. An epinephrine injection is the best-known method of countering anaphylactic shock when it happens.
If you think that you might be allergic to a substance then you should see your GP, who will refer you for an allergy test. Once an allergy is confirmed the best course of action is just to avoid the allergen (the substance that triggers the allergy) as much as possible. Otherwise, in some cases, the reaction can be made less serious by the use of antihistamines, decongestants, moisturising cream or steroid medication.
Severe allergies can be treated in the long term by immunotherapy. This involves controlled and repeated exposure to the allergen in tiny doses so that the body begins to build up a tolerance.
While it is relatively easy, though inconvenient, to avoid eating foods that you are allergic to, it is harder to avoid allergens that are present in the very air we breathe — particularly in the home. Opening a window is the obvious way to let in fresh air, but this can also let in pollen that will worsen an allergy. If you live near a busy road then opening the window will also let in pollution from vehicle exhaust fumes. The best way to deal with the presence of a variety of toxic airborne substances is to use a mechanical ventilation system, fitted by a knowledgeable and experienced installer. This should be used alongside sensible precautions such as removing shoes before entering the home and regularly grooming pets outside of the property.
Dealing with allergies is largely a matter of avoiding exposure rather than treatment after the fact. While science continues to look into the causes, we must all do what we can to reduce our risk in the here and now.