What Is a Histamine Reaction?

Histamine is a chemical (neurotransmitter) that is produced in the body in response to many allergens including pollen, pet dander and more. This is part of the immune response and is what causes allergic reactions to many triggers. Histamine is of course a useful part of the immune response and it works by making the blood vessels in the body larger and easier to penetrate so that the body can swell and protect the area. It is the increase in size of the blood vessels that also additionally creates a reddening of the skin. Histamines are also what cause our skin to go red surrounding a wasp sting. Histamines can also trigger the H1 and H2 receptors which can lead to other symptoms such as headaches and respiratory responses. In some cases histamine reactions can cause asthma in what is called an asthmatic histamine reaction.

Allergic Reactions

A histamine reaction then is an important and normal part of the immune response and can help our body to deal with toxins and to treat infections. However in some cases the body can mistake harmless substances for toxins (a process that can occur at any time in an individual’s life and that is not fully understood). Many people for instance are allergic to a range of pollens, and this is simply because their body has become allergic to something that it should not have. This is where hay fever comes from where the afflicted find their eyes swelling up, itching, watering and becoming red when there is pollen in the air, or their nostrils becoming red and runny. Histamine reactions however are not limited to pollen and can also cause allergies to foods, drinks and many other symptoms.


In some cases a histamine reaction can be so severe as to cause us to go into anaphylactic shock – wherein all of the organs essentially shut down. This can occur in people with anaphylaxis which is an ‘exaggerated’ histamine reaction, meaning that they produce far more histamine than usual in response to things like wasp stings. Early symptoms of anaphylaxis include shortness of breath, edema, wheezing and headache. In such cases it is highly important to get emergency treatment from a health professional.


There are several treatments for histamine reactions. Anti-histamines are medications used to treat such things as hay fever and these work by blocking some histamine receptors. This then means that the histamine is not used by the body and it thus reduces some symptoms. These however do not actually remove the histamine in the body, which can only be achieved using adrenalin. In the case of anaphylactic shock then, an injection of adrenalin will be administered.

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