Cross Allergy | Allergy through amoxicillin

Cross Allergy

In the case of an allergy, an excessive reaction of the immune system occurs after contact with a substance that is recognized as foreign to the body. The immune system orients itself on certain building blocks (antigens). The body now forms antibodies against these building blocks.

These are small molecules that fit the antigens like a key in a lock, so that they clump together and are marked for degradation by macrophages. Different substances, such as drugs, can contain similar building blocks. For example, if the body is allergic to a drug, it can recognise these building blocks even in structurally closely related drugs and react with an allergic reaction. Amoxicillin belongs to the large group of penicillins, which carry a beta-lactam ring to combat bacteria and are very similar in structure. Thus, in case of an amoxicillin allergy, taking other penicillins (e.g. Penicillin G, Penicillin V or Ampicillin) will cause an allergic reaction of the body.

Can an amoxicillin allergy be inherited?

An inheritance of the amoxicillin allergy has not yet been proven. Nevertheless, it is possible that this allergy is more common in a family. In general, a disposition for allergic reactions may exist if the parents also have increased allergies to drugs or other substances. Therefore, if there is the possibility of an allergy to a certain substance, the doctor should be informed in any case. This will prevent complications from arising during treatment with amoxicillin.


In a detailed anamnesis it can first of all be worked out whether symptoms have ever occurred after taking a certain medication (e.g. against the active substance amoxicillin) and how they manifested themselves. A skin test can then be carried out. Similar to the clarification of an allergy to pets or food, the so-called prick test is also used to clarify a drug intolerance.

It is particularly helpful in the case of allergic reactions of the immediate type in order to determine the active substance causing the allergy. The various possible causes are applied to the forearm. The skin is slightly scarred so that the substance comes into contact with the tissue more quickly and a symptom is immediately apparent if an allergy exists.

An intracutaneous test can also be used for clarification, which is similar to the prick test, but the drugs are injected into the subcutaneous layer of skin. If these tests are unsuccessful and no substance can be identified as responsible for the allergy, there is still the possibility to perform a provocation test. In this test, small amounts of the possible allergenic drug (in this case: amoxicillin) are administered.

In this way it can be observed to which active substance the patient clearly reacts. However, this test should only be carried out under strict observation and if no serious reactions are to be expected, as an anaphylactic shock is a life-threatening situation. Furthermore, various blood tests can also be performed.

In case of an allergic reaction the body produces antibodies of the IgE type, which are typical for an immediate reaction. If they are elevated in the blood, this can be an additional indication. In addition, tryptases can also be found in the blood in increased amounts. They belong to the mast cell activating mediators and are therefore elevated in the blood during an acute or already experienced allergic reaction.