An allergy occurs when our body reacts to a substance that is actually harmless but is recognised as ‘dangerous’ by the immune system.

How does an allergy develop?

• The first contact with this substance causes ‘sensitisation’ – in other words, the immune system learns to recognise this substance.
• The next time we come into contact with the same substance, an allergicreaction may occur. Certain antibodies (e.g. IgE antibodies) are involved in this process.
• Sometimes a tiny amount of this substance is enough to trigger a reaction.
• The reaction can be very mild (e.g. itching) or very severe (e.g. circulatory or respiratory arrest).
• A distinction is also made between immediate reactions and delayed reactions.
• Whether someone develops an allergy depends on various factors, such as predisposition (genetics) and the environment.

Common allergy triggers (allergens)

• Foods (e.g. peanuts, soy)
• Medicines (e.g. antibiotics, vaccines)
• Substances that are inhaled (inhalation allergens) – e.g. pollen
• Insect venoms (e.g. bee venom)

Cross-reactions

In some cases, people also react to substances that are similar in structure to a known allergen – this is called a cross-reaction.

If you know that you have an allergy or drug intolerance, you should inform your doctor or pharmacist.

Pseudoallergy / intolerance

There are reactions that are similar to allergies but do not involve the immune system – these are called “pseudoallergies” or “intolerances”.

• In a pseudoallergy, there is no sensitisation phase, and the immune system is not involved.
• In the case of intolerance, the reaction depends on the amount – the more you ‘get’ of it, the greater the reaction.
• An example: Some people have a deficiency of an enzyme (e.g. lactase). When they consume milk sugar (lactose), they may experience discomfort – even with medicines or foods containing lactose.

What should you bear in mind if you have a drug intolerance?

If you know that you cannot tolerate certain drugs or ingredients, please note the following:

• Inform your doctor or pharmacist about this.
• Before taking or using a drug, be sure to read the package insert (leaflet).
• Section 2 of the package leaflet states the circumstances under which the medicine must not be taken.
• Section 6 (‘Contents of the pack and other information’) lists all the active ingredients and excipients in the medicine.
• The outer packaging does not always contain a complete list of all ingredients – this is because the packaging may be very small, for example.