What Causes Allergies – A Beginner’s Guide

 When someone has an allergic reaction, what is really happening?  You might wonder how so many different things seem to be able to create the same reaction. Read on to get the lowdown…


What happens to the body during an allergic reaction?

Allergies start when your body mistakes a harmless substance to be a harmful intruder.  Normally our immune system sits on guard to stop harmful substances from staying in our body when they enter it.  The immune system gets rid of bacteria and viruses, along with other substances that just do not belong in our body.  When it is doing its job correctly, our immune system will keep us from getting sick most of the time.allergy nasal symptom

Sometimes the immune system has a difficult time determining whether something is a threat or not, and makes the mistake of calling a totally harmless substance something that needs to be attacked and gotten rid of.  It decides to attack food proteins, dust, pollen, or animal dander – simple things in our environment that really won’t hurt us.  That’s when you have an allergic reaction to deal with and when the average environmental substances get called allergens.


IgE antibodies

When people who have allergies come in contact with an allergen their immune system produces antibodies, called IgE antibodies, against the substance.  These antibodies join onto the surface of the “mast cells” and sit in wait for the next time the allergen shows up.  While waiting the mast cells fill up with lots of proteins that will help in defense of the body when the right time comes.  When the allergen shows up again, it binds to the IgE on the surface of the mast cells.  The mast cells in response pour the proteins into the person’s system.

One of these proteins is histamine.  You may have heard of it, or you have heard the word antihistamine, a drug that can work against histamine.  Histamines are the big player in allergic reactions as the body reacts with the symptoms we associate with allergies such as a runny nose, itchy eyes or skin, coughing or sneezing, and watery eyes.  Your skin could pop up hives and you could throw up something that you swallowed that you are allergic to.

All these reactions are trying to get the allergen out of the body.  They can help most if the allergen is in the air and coming into our body via the nose and eyes, but vomiting a piece of food your body is allergic to can be just as helpful.



Allergic reactions can have two phases.Woman with allergy remedy treatments

The first happens quickly, within the first few minutes of exposure.  It is caused by the release of proteins, mainly histamine, from the mast cells.

The second phase happens later and is caused by inflammatory cells that are recruited to come into the area and continue the attack.  The later phase can lead to more skin reactions such as rashes and eczema.  The later phase of an allergic reaction can also include digestive system problems like diarrhea and an extended upset stomach, headache, fatigue, and just feeling lousy.

Allergic reactions can become very serious when they involve anaphylaxis.  Anaphylaxis is the body’s severe reaction  to an allergen.  It can start out looking mild enough with a skin rash and watery eyes and nose, but then the person can develop difficulty swallowing as the airways swell up from nose and mouth to lungs.  Heart rate can increase tremendously while blood pressure drops.  This is all in response to the mediator proteins, especially histamines, that are released by mast cells and other related cells in response to the allergen.  At this point the person needs medical help as quickly as possible.


More on causes

Allergies can happen at any age.  Even babies and children can have allergies.  Many times their allergies show up as skin conditions but they can have watery eyes and runny noses too.  What causes allergies later in life are the same things that can cause them when we are young, but as we age we are exposed to more and more possible allergens giving our body a chance to react.  Our bodies also change with time and something that our body did not consider a problem could become an allergen of interest.  What makes these changes remains a question.

You might wonder what causes seasonal allergies because you suffer significantly every spring or each fall, or every time someone mows their lawn.  The vast majority of seasonal allergies are nasal allergies.  Your body is reacting to allergens being released by plants.  You might react to a pollen that is released at the plant’s time to pollinate and reproduce.  The pollen is released into the air in search of the “other plant” that it needs to come in contact with to continue the growth and replication of the plants.  You could react to the bits of grass that are in the air after cutting it.

Allergies to cats and dogs are allergies to their hair, dander (essentially shed skin cells), saliva, and even urine.  Your body happens to consider them an intruder, not a friendly cell that won’t hurt you.  It makes the IgE against the substance and is ready to fight with histamines and other proteins when the substance presents again.  Signs of the battle remain the same—watery itchy eyes, runny nose, skin rash.nuts

With seasonal or animal allergies you are not exposed to the allergen on a continuous basis.  You either end up exposed because of the time of the year, or because you happen to be near an animal.  These allergies point out how you must be exposed to the allergen in order to have the reaction.  Stay away from the plants or animal and you won’t have an allergic reaction.  Allergy reactions can feel as though they happen without a protagonist, but they probably really can’t, we just don’t know what and where the cause is.

Allergies can be unpredictable.  Most times the first exposure to an allergen causes no reaction or a very mild reaction.  Reactions after that can be variable, and you may not be able to see why.  The amount of allergen you are exposed to may play a role, but sometimes a full scale attack is run with exposure to very little allergen.

One very important concept here:  can someone be allergic to housework?  Sure, they can be allergic to the dust mites and spores that are stirred up from dusting and vacuuming the house.  Just be sure they are being honest about the true allergy!  Most “housework allergies” are dislike of the work, not a true physical reaction!


It is difficult to think that our body’s natural defense system can attack something that is totally benign and cause such a problem, but it happens.  Allergies are a symptom of over performance by the immune system.  If you think about it, maybe it is better to have an allergy than a poorly performing immune system, but many times it is hard to convince ourselves of this when we are in the middle of all the symptoms of an allergic reaction.

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