What are the different types of allergies?

Two criteria are used in determining which group an allergy belongs to:

first, the reaction mechanism, and second, the reaction time – how long it takes for symptoms to appear.

• Type I - Immediate reaction (also known as anaphylactic reaction)
• Typ II - Cytotoxic
• Typ III - Immune complex allergies
• Typ IV - Delayed-onset allergies, cellular immune reaction

This type of allergy is characterised by the immediate onset of symptoms (within seconds or minutes). Usually, the skin or mucous membranes are affected. Almost all Type I allergies are caused by proteins. Type I allegies are the most common allergies.

Beispiele sind:

• Hay fever (allergic rhinitis)
• Animal hair allergy
• Insect venom allergy
• Latex allergy
• Dust mite allergy
• Food allergy
• Medication allergy (local anaesthetics, antibiotics)
• Allergic asthma
• Urticaria
• Quincke's edema
• Anaphylactic shock

A Type II allergy means the body’s own cells have been damaged, and are treated as allergens by the immune system. Specific antibodies bind directly with the cell surface, turning the cell into an antigen that must be attacked.

Type II allergies are rare.

Examples of Type II allergies:

• Blood transfusion reactions
• Autoimmune haemolytic anaemia
• Myasthenia Gravis
• Agranulocytosis
• Blood group intolerance

Medication allergies are often type-III reactions. Foreign substances in the blood – such as medication – bond with antibodies, and then with the blood vessel walls in the smaller blood vessels, for instance, in the skin or kidneys. This leads to local inflammation, for instance, a skin rash, often in conjunction with haemorrhaging, skin damage, and itching.

Typical Type III allergies include:

• Vasculitis (inflammation of the blood vessels)
• Serum illness 
• Alveolitis, Farmer’s Lung
• Nephritis (inflammation of the kidneys)
• Arthritis (inflammation of the joints)

Type IV allergies are characterised by the delayed allergic reaction. As with Type II allergies, allergens bind with cells, activating certain T-Lymphocytes, which recognize and attack these cells. This leads to damage in the surrounding tissues. This first contact sets off an immune reaction; whenever the T-lymphocytes encounter this allergen, it sets off a major allergic reaction. Because the (re-)activation of the T-lymphocytes takes some time, the allergic reaction first occurs 12 to 72 hours after contact with the allergen. 

Typical Type IV allergies:

• Transplant rejection
• Contact allergies (e.g. nickel allergy)
• Tuberculin reaction (Tbc-Test)
• Rashes due to medication allergy