Most allergies are inherited, which means they are passed on to children by their parents. Although people inherit a tendency to be allergic, they may not inherit an allergy to the same allergen. When one parent is allergic, their child has a 50% chance of having allergies. That risk jumps to 75% if both parents have allergies.

Typically, an allergic response is not triggered the first time the body encounters the allergen. The first, or several times after the body is exposed to an allergen, the immune system becomes sensitized and prepares to react to the next encounter with the allergen. Once sensitized, the immune system can quickly detect the drug in the body and produce immunoglobulin E (IgE). These antibodies trigger the release of chemical mediators, including histamine, which may cause allergic symptoms up to and including anaphylaxis.

Common allergy triggers include pollen, dust mites, molds, animal dander, latex, foods and insect venom.

Common allergy symptoms include runny nose, tearing eyes, burning or itching eyes, red or swollen eyes, coughing, wheezing, difficulty breathing, hives, skin rash, stomach cramps, vomiting, diarrhea, headache and itchy nose, postnasal drip, impaired smell, as well as itchy mouth, throat or skin.

Skin test: A skin test is used to determine whether a patient is allergic to certain substances, such as mold, dust mites or animal dander. During the test, the skin is exposed to different allergy-causing substances (allergens) and then observed for an allergic reaction. Some tests, like the percutaneous (puncture, prick or scratch) test, detect immediate allergic reactions, which develop within minutes of exposure to an allergen. Other tests, like the epicutaneous (patch) test, detect delayed allergic reactions that develop over the course of several days. If an allergen triggers an allergic reaction to a test, the patient will develop reddening, swelling or a raised, itchy red wheal (bump) that looks similar to a mosquito bite. The healthcare provider will measure the size of the wheal and record the results. The larger the wheal, the more severe the allergy.

Radioallergosorbent test (RAST): An allergen-specific immunoglobulin E (IgE) test, commonly referred to as radioallergosorbent test (RAST®) is a type of blood test that can help determine if a patient who experiences allergy symptoms, such as runny nose, watery eyes and hives, is allergic to particular substances called allergens.

The in vitro test (performed outside of the body, in a laboratory setting) exposes a blood sample to suspected allergens (like dust mites, pollen or animal dander) to determine whether the patient has developed allergen-specific immunoglobulin E (IgE) antibodies. Antibodies are proteins that recognize and bind to specific antigens.

During the procedure, a sample of blood is taken from the patient. The blood is then sent to a laboratory that performs specific IgE blood tests. An allergen-antigen complex is bound to an allergosorbent (paper disk) and the patient's blood is added. If the blood contains antibodies to the specific antigen, it will bind to the "tagged" immunoglobulins.

RAST® is less accurate than a skin test. However, if the patient has a severe skin disease (like eczema or psoriasis) that is present on large areas of skin on the arms or back, a skin test may not be possible. This is because the skin test may only be performed on the arms and back, and there may not be enough unaffected skin to perform a conclusive test. For these patients, an allergen-specific IgE test is the preferred diagnostic method.

Anaphylaxis is a rapid, immune-mediated (allergic), systemic reaction to allergens (like food, medication or insect stings) that the individual has previously been exposed to. Anaphylaxis is a medical emergency that requires immediate medical treatment, as well as follow-up care with an allergist or immunologist. Symptoms of anaphylaxis can vary from mild to severe and may be potentially life threatening. The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal. Epinephrine is a medication used to treat anaphylaxis. Administering the epinephrine as soon as possible improves the chances of survival and a quick recovery.

Individuals who have a history of anaphylaxis should carry an autoinjectable epinephrine device (EpiPen®) with them at all times. If symptoms of anaphylaxis appear after exposure to an allergen or medication, the patient uses the device to inject the epinephrine into his/her thigh. A trained family member or friend may help the patient administer the epinephrine, if necessary.