Suppression

Histamine

Category: Natural chemicals

Type

Voluntary

Introduction and description

 

Histamine is a neurotransmitter that helps us fight pathogens and helps to regulate the inflammation response – part of the non specific Immune system.

The sequence of the response mechanism to pathogens and histamine is just a part of the immune response.  When a foreign pathogen enters the system, histamine is released by  ‘basophils’ and by ‘mast cells’ found in connective tissues near the site of entry.  Histamine therefore doesn’t fight the pathogens, but histamine is part of that system.   Histamine:

  • dilates post capillary venules - A venule is a small blood vessel in the microcirculation that allows deoxygenated blood to return from the capillary beds to the veins.  So here the objective is to open up the main channels by which the defences can reach the site of attack
  • activates the endothelium - The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood and the rest of the vessel wall. Endothelial cells line the entire circulatory system, from the heart to the smallest capillary. These cells reduce turbulence of the flow of blood, allowing the fluid to be pumped farther.  Again, the aim is to allow the blood to be pumped to the site more easily speeding the rate at which protective defences can reach the site of attack
  • and increases blood vessel permeability - Increased vascular permeability causes fluid to escape from capillaries into the tissues, it is what produces the swelling and the classic symptoms of an allergic reaction: a runny nose and watery eyes, although both are protective measures intended to wash away the pathogen.
 

Essentially, therefore, histamine may produce some unpleasant symptoms, but they are effects that are actually in our best interest.  We may experience  local oedema (swelling), warmth, and redness, but what we are also getting is the attraction of anti-inflammatory cells to the site of release.

Histamine also irritates nerve endings leading to itching or pain. This may seem barmy because why should we have to experience pain?  But of course we need to know that a particular pathogen is harmful so that we both stop what we are doing and give the body a chance to heal itself, whilst avoiding whatever it is that is attacking us.  It is a signal to the brain to warn us of the danger.  ‘Slow down’ it says, ‘take a break’ or ‘keep away’.

So histamines are essential for our well being.

see Antihistamines

References and further reading

Photos by Jenny Soppet Smith

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