Allergic reactions are an overreaction of the body’s immune system to specific substances, which are called allergens. Allergens are usually proteins, and can come from many different things such as pollens, foods, house dust, moulds or some medications. When the body encounters these substances, the immune system responds as if they were toxic, and launches an attack.

Common allergic reactions include eczema, hives, hay fever, asthma, food allergies and reactions to the venom of stinging insects such as wasps and bees. Mild allergies like hay fever are highly prevalent in the human population and cause symptoms such as itchy eyes and runny nose. Allergies can also play a major role in conditions such as asthma. In some people, severe allergies can result in life-threatening anaphylactic reactions and potentially death.

A variety of tests are now available to diagnose allergic conditions, which include testing the skin for responses to known allergens or analysing the blood for the presence of allergen-specific molecules. There are many treatment options to combat allergies, which include immunotherapy, allergen avoidance and the use of medications. Specially designed bracelets are also readily available for people with allergies to wear, which provide information about their allergy in case of emergencies.

Signs and symptoms

The symptoms of allergic reaction vary dramatically depending on the type of allergen and the part of the body that is affected, but common allergy symptoms include:-

· Nasal swelling
· Itchy or red eyes
· Sneezing, coughing, wheezing and shortness of breath
· Asthma attacks
· Painful or blocked ears, which can impair hearing
· Swelling, especially of the tongue, mouth or eyelids
· Skin rashes, such as eczema and hives
· Abdominal pain and bloating
· Nausea and vomiting
· Diarrhea
· Tingling and itching in or around the mouth

Different types of allergies

Allergies are common and people can have reactions against a range of irritants. Some of the different type of allergies people experience include:-

Hay fever is an allergy that affects the nose and it occurs most common in spring when the amount of pollen in the air is very high. Hay fever can also be caused by dust mites, moulds or animal hair. People with hay fever get a runny or stuffy nose, itchy eyes and throat, watery eyes, headaches and sneezing. These symptoms are a result of the allergic reaction the body has to the particles trapped in the nose when they breathe.
Food allergies occur when people are sensitive to certain types of food such as nuts and shellfish. The symptoms of food allergy can include skin rashes, vomiting, breathing difficulties and itching or swelling around the mouth. Food allergies can be severe or even life threatening. Nuts, eggs, milk and soy cause about 90 per cent of food allergies, and peanut allergy is one of the most common allergies found in older children. Other common causes of food allergy include sesame, gluten, fish, grains and food additives such as MSG.
Dust allergies are cause by a type of mite, which live in household dust. Dust is composed primarily of skin flakes, which we shed regularly and these are what dust mites like to eat. Areas around the home that are heavily used, such as beds and upholstered furniture, have very high mite populations compared to the rest of the house. The symptoms associated with dust mite allergy include itchy nose, eyes or skin, wheezing, coughing and breathlessness. Dust mites like to live in humid and dark environments, and they are commonly found in mattresses and bed linen, furniture, carpet and soft-toys. If a person in your household suffers from dust allergies, then the best ways to help control their symptoms are to wash sheets and pillowcases weekly in hot water, vacuum regularly and to clean hard surfaces with cloths that remove the dust rather than a feather duster.
Mould allergies are often caused by a common type of fungus called Aspergillus. This fungus is found growing on decaying vegetation, such as compost heaps and fallen leaves, and can also be found in air conditioning systems and hospitals. Mould allergies are often a trigger for asthma, and cause symptoms such as wheezing and breathlessness. In rare cases, people can suffer lung or other organinfections with Aspergillus. People at risk of developing Aspergillus infections are those who are severely ill, or those with poor functioning immune symptoms.
Drug allergies occur in people who have reactions to medications such as aspirin and antibiotics such as penicillin. Allergic reactions to drugs range from mild skin rashes to severe effects on the liver and kidneys. Drug allergies may cause many different types of symptoms depending on the drug and the degree of exposure. The most common reactions include hives, sensitivity to light, fever, swelling, breathing difficulties, and muscle and joint aches.

Latex allergies occur in people who are allergic to the chemical used in the manufacture or the natural proteins in latex, which is a type of rubber. Between 1 and 6 per cent of people are though to suffer from latex allergies. There are many products that are made from latex including rubber bands, balloons, gloves, dummies, condoms, catheters and stethoscopes. The symptoms of latex allergy range in severity depending on the individual, but can include dermatitis, itchy skin, hay fever symptoms and breathing difficulties. Latex allergies become most evident in people who are frequently exposed to latex through medical equipment like gloves, such as doctors, dentists and nurses. Interestingly, approximately half of all people with latex allergies also have allergic reactions to foods including banana, strawberry, kiwifruit, avocado, chestnut, passionfruit, plum and tomato, which is because some of the proteins in the latex responsible for allergy are also present in these foods.


A wide variety of substances can cause allergic reactions. Allergy testing is the procedure used to determine which of these particular substances (allergens) are responsible for provoking a reaction. While the procedure used depends on the type of allergy, they often include skin and blood tests or special diets.

Skin prick tests involve the application of selected allergens to the skin, and the skin is gently pricked with a needle. Common areas for testing include the back and the inside of the forearm. Allergens can also be injected into the skin using a needle. An allergic reaction is characterised by a visible inflammatory reaction that usually occurs within 30 minutes. This response will range from a slight reddening of the skin to a severe outbreak of hives.

Patch tests are most commonly used to investigate dermatitis. Patches containing common triggers are applied to the back in adhesive strips. The area is then examined after 2 to 4 days, where a positive result is shown by redness or blisters at the site where a particular substance was applied.
Blood testing can be used to detect allergies to specific substances by measuring the amount of IgE, a molecular produced by the body in response to allergic reaction. A person with allergies will usually have a higher IgE level than the average person who does not suffer from allergies. Blood tests are most useful when skin testing is not possible or is inconclusive.
Elimination diets are used to isolate foods that may be causing the allergic reaction. This usually takes a number of weeks and involves avoiding foods identified as common causes of food allergy. If symptoms improve, foods are added one at a time until symptoms recur. This way the specific food that results in allergy can be identified. It can be useful to keep a diary during this process to record what you eat and any symptoms, so they can be linked to the correct food.


They are many treatment options available to reduce the symptoms associated with allergies, some of which include:-
Eye drops. These may relieve itchy, swollen or runny eyes.
Corticosteroid nasal sprays. These to help reduce inflammation in the nose, which is the cause of nasal blockage and runny noses.
Anti-histamine medications. These are non-drowsy medicines that may be useful in controlling sneezing and itching.
Immunotherapy. This form of treatment involves exposure to increasing amounts of allergen, which enhances the resistance of the immune system, improves tolerance and reduces the symptoms associated with that particular antigen. This therapy can be useful for reducing hay fever and some cases of asthma, but does not help food allergies.
Avoiding the antigen. For example if you have latex allergies, then choose synthetic rubber products, or avoid foods that trigger symptoms, and keep your house free from dust.

Anaphylaxis can be a dangerous complication of allergies, and is a severe, whole-body allergic reaction. Peanuts, other nuts, insect stings and some medicines are the most common allergens that cause anaphylaxis. Symptoms of anaphylactic shock include hives and swelling of the lips, eyelids, throat and tongue, which block the airways and can cause suffocation. Other symptoms include collapse and loss of consciousness. While this type of reaction is rare, it is life-threatening. People who are at risk of anaphylaxis often carry self-injectable syringes of adrenaline called Epi-Pens, which are available from pharmacies. Administering adrenaline using the Epi-Pen prevents further injury or death, and can be given by the person themselves or another individual in case of anaphylaxis.