Allergies occur as a result of a reaction of the immune system to a foreign substance such as pollen or bee venom that does not usually trigger a reaction in most people.

The immune system produces antibodies that identify certain allergens as harmful even though it is not. Any contact with the particular allergen causes an immune system reaction that can inflame the skin, sinuses, airway or digestive system.

The severity of allergies varies among people ranging from minor irritation to life-threatening anaphylaxis.

Most allergies cannot be cured, although many treatments are available to relieve and manage the symptoms.


Allergy symptoms vary according to the substance but they usually affect the skin, airways, nasal passages and digestive system. In rare and severe cases some allergies can trigger a life-threatening anaphylaxis.

Symptoms of hay fever (allergic rhinitis):

  • Sneezing
  • Itching of the nose, eyes or roof of the mouth
  • Runny/stuffy nose
  • Watery, red or swollen eyes (conjunctivitis)

Food allergy can cause:

  • Tingling mouth
  • Swelling of the lips, tongue, face or throat
  • Hives
  • Anaphylaxis

Insect sting allergy can cause:

  • Large swelling (edema) at the sting site
  • Itching or hives on the body
  • Cough, chest tightness or shortness of breath
  • Anaphylaxis

Symptoms of a drug allergy include:

  • Hives
  • Itchy skin
  • Rash
  • Facial swelling
  • Wheezing
  • Anaphylaxis

Symptoms of atopic dermatitis (allergic skin condition known as eczema):

  • Itching
  • Skin redness
  • Flaking or peeling of the skin


Some allergies (foods and insect stings) can trigger a reaction called anaphylaxis. It is a severe life-threatening reaction that can make a person to go into shock.

Symptoms of anaphylaxis:

  • Loss of consciousness
  • Drop in blood pressure
  • Lightheadedness
  • Severe shortness of breath
  • Rapid, weak pulse
  • Skin rash
  • Nausea and vomiting


The immune system produces antibodies for particular allergens. Any contact with the particular allergen causes the antibodies to trigger a reaction through releasing immune system chemicals such as histamine. This immune system reaction causes the allergy symptoms.

The common allergy triggers are:

  • Airborne allergens (pollen, animal dander, dust mites and mold)
  • Foods (peanuts, tree nuts, eggs, milk, fish, soy, shellfish, wheat)
  • Insect stings (bee or wasp stings)
  • Medications (mainly penicillin or penicillin-based antibiotics)
  • Latex or other substances that can cause allergic skin reactions

Risk factors

The following factors can increase the risk of developing an allergy:

  • Family history of asthma or allergies: A family history of asthma or allergies such as hay fever or eczema can increase the risk of allergies.
  • Asthma or an allergic condition: Asthma increases the risk of developing an allergy. Moreover, having one type of allergy increases the likelihood of being allergic to something else.
  • Children: Children are at a greater risk of developing allergies than adults. However, sometimes children can outgrow allergic conditions.


Allergic conditions can cause other medical problems or complications including:

  • Anaphylaxis: Severe allergies can trigger a life-threatening reaction known as anaphylaxis. The most common triggers are food, penicillin and insect sting allergies.
  • Asthma: The likelihood of having asthma is greater with an underlying allergic condition. Asthma is also an immune system reaction that affects the airways and breathing. Allergy induced asthma is typically triggered by exposure to an allergen in the environment.
  • Eczema, sinusitis and infections of the ears and lungs: These complications can arise as a result of having hay fever, a pet or mold allergy.
  • Fungal complications of the sinuses or lungs: Mold allergies can increase the risk of developing fungal sinusitis and allergic bronchopulmonary aspergillosis.


Some of the methods to prevent an allergic reaction include:

  • Avoiding allergens: If the allergen is identified, one should avoid triggers as much as possible even during treatment.
  • Diary: Keeping a diary of activities when symptoms occur can identify triggers, causes or factors that influence the symptoms. This can help in gaining a better understanding of what triggers the allergic reaction.
  • Medical alert bracelet: Wearing a medical alert bracelet may be necessary for people who suffer from severe allergic reactions. The medical bracelet serves to alert other of the serious condition in the case that the person is unable to communicate.