Click here to see in dynamic what happens in the acute allergic attack or come back after you have red the detailed description of this process written below.
The acute allergic attack is directed by the mast cells armed with IgE and in most allergic persons, regardless of their disease, the first symptoms they feel when coming in contact with the allergen are caused by the histamine released from the mast cells.
As said above sensitization is in fact only a preparation of the mast cell to be able to recognize and to react when the allergen is attacking the body.
In people who develop allergic symptoms, IgE attached on the surface of the mast cells recognize and bind to the allergen every time we come in contact with it.
When the allergen is bound on the IgE, a signal will be triggered alerting the mast cell about the presence of the so called aggressor, pushing them to step in action in an effort to stop the invader. Consequently the mast cell starts firing with histamine and the other substances stored inside its granules. Histamine causes changes that on one hand makes the environment hostile for the allergen while on the other hand helps the specialized forces to get to the conflict place. Many of the symptoms you feel during the allergic attack are caused by the changes induced by histamine:
- Histamine causes dilatation (enlargement) of the blood vessels.
If the body would be truly attacked by an aggressor this effect
would be very important because it would allow more blood to get to
the battle area, and consequently would increase the force fighting
with the enemy (because the blood is bring more soldiers and
weapons- cells and antibodies). However, in allergy this effect
only causes unpleasant symptoms without having a useful side. How
will you perceive this effect? You will not be able to see your
dilated blood vessels but you might notice a redness of the organ
affected by allergy:
- if you have urticaria you may notice that the skin affected by the wheals is more red than the normal skin
- if your have allergic conjunctivitis you might have noticed that during an allergic attack your eyes are more red than usual
- if you suffer from allergic rhinitis or asthma dilatation of your blood vessels will also cause redness of your nasal or airway mucosa, but since these linings are not on sight you will not be able to notice them.
- Histamine makes the walls of your blood vessels more permeable.
All The helpers brought by the blood have to cross the blood vessel
walls in order to reach the battle place. To help crossing this
wall, histamine creates small gaps in it through which the useful
liquid substances in the blood can pass much easy. Now, with all
these liquids getting out of the blood, the tissues will be soaked
and they will get swollen. You can guess which of your annoying
symptoms are due to this effect of histamine:
- in urticaria the swellings of the skin tissues cause the wheals that you experience during the urticaria attack
- in allergic rhinitis this causes a swelling of the nasal mucosa which contribute to the narrowing of the nasal air passages and to the sensation of nasal obstruction
- similarly, in asthma this causes a swelling of the lining of the airways. This contributes to their narrowing and consequently to your breating difficulties (however this is a minor contribution and you will see later that there are more important factors that make you breath difficultly)
- Histamine getting in contact with your nerves tickles
(irritates) them – this initiates various protective reflexes all
of which aim to help expelling the aggressor from the body. If this
reaction of the immune system would be mounted against a true
aggressor, each one of these reflexes would be very useful.
However, in allergy the body is fighting with a false aggressor and
these reflexes from useful protective actions become annoying
symptoms.
- in urticaria it causes itching, a reflex through which the body tries to remove the aggressor present on the skin
- in allergic rhinitis it causes itching and sneezing. These reflexes aim to expel the allergen that has entered inside your nasal cavity
- in allergic conjunctivitis it causes itching of your eyes
- in asthma it causes coughing
- in the intestine tickling of the nerves accelerates the intestinal transit and may lead to cramps and diarrhoea
- Histamine stimulates the production of mucus in the organs where the mucus glands are present (such as nose, airways, digestive tract). Once again this is a very important effect in case of the attack of a true aggressor because it would help to wash out the aggressor; however in allergy it results again in bothersome symptoms:
- In allergic rhinitis it causes runny nose
- In allergic conjunctivitis – tear formation and lacrimation
- In asthma it causes your bronchi to produce phlegm which stimulates cough (you cough because you try to get rid of the phlegm). Also phlegm contributes to the narrowing of the air passages and therefore to the breathing difficulties you experience during an asthma attack.
- Histamine stimulates the muscles in the airways and in the gut to contract
- In asthma this causes an important narrowing of your air passages which is the most important cause that makes you feel breathless.
- In the gut this causes spasms which you perceive as abdominal cramps