Allergic rhinitis is the most common symptom

Do you know how many types of allergy there really are?

Hay fever, pet and house dust mite allergies are very common. Other manifestations, such as allergic alveolitis, are far less common. This page briefly addresses the various forms.

Allergic rhinitis, the most common symptom, occurs in two forms, the seasonal type and the non-seasonal type. Seasonal allergic rhinitis is better known as hay fever. Symptoms of allergic rhinitis include sneezing, watery or irritated eyes, a blocked or runny nose and flu-like feeling. The symptoms occur during the flowering season of trees, grasses or shrubs, when they release pollen into the air, hence the term 'seasonal'. When the season is over, the symptoms disappear as well. Non-seasonal allergic rhinitis may occur all year round, its symptoms are comparable to the seasonal type but the allergens are different. Examples of this type of allergy are house dust mite and pet allergy.

Allergic conjunctivitis is an inflammation of the conjunctiva of both eyes. It is characterised by red, tearing and itching eyes. This type often goes hand in hand with allergic rhinitis.

Asthma occurs in many different forms. Allergic asthma is a fairly common type. It is a process of respiratory inflammation caused by inhaling substances to which one is allergic. Initial complaints include frequent coughing, respiratory infection and fatigue. Typical symptoms such as wheezing and shortness of breath occur at a later stage.

Allergic alveolitis is a collective name for a number of allergic pulmonary disorders caused by minuscule substances, often fungi and animal proteins. These substances are so small that they can enter the airways, where they cause an inflammatory reaction. Alveolitis is fairly rare. An example is pigeon fanciers lung, a disorder caused by extremely small dust particles in the droppings in a dovecote.

Urticaria is also known as hives or nettle rash. It is an allergic skin disorder characterised by severely itching lumps or rashes. Those rashes may occur anywhere on the body, occasionally causing a burning and chafing feeling. It has many causes, ranging from foodstuffs to detergents, from skin care products to even sunshine. Sun allergy is a form of urticaria, for example.

Angio-oedema is a special type of urticaria or nettle rash. The itching is considerably less severe, but the lumps accompanying angio-oedema are much bigger than those associated with urticaria. Angio-oedema often manifests itself on the eyelids, lips and mucous membranes.

Eczema is a skin disorder characterised by fluid-filled vesicles on the skin. The vesicles burst, which is followed by crustation. Eczema is a prevalent disorder, but may also have non-allergic causes.

Allergic eczema is divided into 'atopic eczema' and 'contact eczema'. A symptom of atopic eczema is an allergen-induced eczema-like rash. This is referred to as 'atopic', which means 'prone to allergic reaction'. Atopic people tend to have hay fever and asthma and (atopic) eczema.

If you suffer from contact eczema, you will by definition have other allergic symptoms. Contact eczema does not discriminate. It arises in places where the skin has been in contact with an allergen. An example is allergy to nickel or chrome, which is found in certain jewellery and watches.

An insect allergy can be triggered by insect stings. Wasp stings in particular may evoke severe allergic reactions. Skin reactions are frequent, but respiratory problems may occur as well.

An occupational allergy is an allergic reaction to a substance present in the workplace. Occupational allergies are often contact or inhalation allergies. Complaints generally develop over time. Examples are allergies to animals or allergic reactions to chemical substances. The symptoms of an occupational allergy are extremely diverse and depend on the type of allergen. A well-known occupational allergy is hairdresser's eczema: an allergic reaction to contact with perm liquids or hair dyes.

If you are allergic to birch pollen, you may also react allergic to eating hazelnuts and apples. This may seem curious but it is one of a great many examples of what is known as cross allergy.

An allergy is called a cross allergy if the antibodies that the body produces against one allergen, start reacting to another allergen as well, for the simple reason that they are alike. They are related to each other, family, so to speak. Appearance does not enter into it: hazelnuts, apples and birch trees do not look like each other, but they contain related allergens, as do kiwi, pineapple and potato, for instance.

An anaphylactic shock is an extremely severe allergic reaction of the entire body. The reaction may occur very quickly, within minutes. An anaphylactic shock is a dangerous reaction of the body, which may be life-threatening. The body reacts very strongly to an allergen. Not just in one place, for instance the site of a wasp sting, but spread across the entire body. Such a strong reaction may cause a substantial drop in blood pressure and lead to loss of consciousness. Severe swelling of the pharynx, may cause tightness of the chest. A shock reaction to a particular kind of food may involve severe nausea, followed by vomiting and abdominal cramps. Without rapid treatment, the pulse will begin to race, which may lead to loss of consciousness.

It is therefore essential that the attack be treated as quickly as possible. The most common causes of anaphylactic shock are insect stings, particularly by wasps, and food ingredients (especially peanuts). Such a reaction virtually never occurs with pollen, pet or house dust mite allergies.

The symptoms of an anaphylactic shock reaction may be the same as those associated with other allergic reactions, but are generally much more severe. Symptoms that often accompany a shock reaction are laboured breathing, dizziness, arrhythmia, bright redness of the skin and vomiting.

Not all cases of hypersensitivity to food are allergies. The difference between food allergy and food intolerance is that the former is related to our immune system, whereas intolerance is not. Food allergy is an allergic reaction to certain foodstuffs, such as peanuts. Food allergy often comes paired with gastrointestinal problems, nausea, vomiting, diarrhoea, but also skin complaints or respiratory problems.