General: An allergy, or hypersensitivity reaction, occurs when the body's immune system overreacts to a substance that is normally harmless (allergen). Common allergy triggers include pollen, dust mites, molds, animal dander, latex, foods, and insect venom.

The white blood cells of an allergic individual produce an antibody called immunoglobulin E (IgE), which attaches to the allergen. This triggers the release of histamine and other inflammatory chemicals that cause allergic symptoms, such as runny nose, watery eyes, hives, angioedema, and atopic dermatitis. The most severe allergic reaction, known as called anaphylaxis, can lead to low blood pressure, breathing difficulties, shock, and loss of consciousness, all of which can be fatal.

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 has allergies, each of his/her children has a 50% chance of developing allergies. That risk increases to 75% if both parents have allergies.

Allergic rhinitis: Pregnant women with allergies often suffer from seasonal allergic rhinitis, also called hay fever or nasal allergies, which occurs when airborne allergens like dust, dander, or pollen are inhaled. Allergic rhinitis is characterized by a collection of allergic symptoms, predominantly in the nose and eyes. When pollens cause the allergic symptoms, the allergic rhinitis is commonly referred to as hay fever. Perennial allergic rhinitis is an allergic reaction that has little or no seasonal variation. It is persistent, chronic, and generally less severe than seasonal allergic rhinitis.

Non-allergic rhinitis (rhinitis of pregnancy): Non-allergic rhinitis appears to be caused by an increase in pregnancy hormones, including estrogen and progesterone.

Allergic asthma: Pregnant women often suffer from allergic asthma, which occurs when allergens cause the airway to become inflamed. Asthma is one of the most common, potentially serious medical problems that occurs during pregnancy. According to some studies, asthma may complicate up to seven percent of all pregnancies. If asthma is not controlled, the mother has lower levels of oxygen in her blood. This may result in decreased oxygen in the fetal blood, which may also cause growth deficiencies in the fetus or death.

Pregnant women with asthma have an increased risk of delivering prematurely or giving birth to an infant with low birth weight. In addition, pregnant women with asthma are more likely to experience high blood pressure or a related condition called pre-eclampsia (swelling, high blood pressure, and kidney malfunction).

Proper treatment and management of asthma symptoms may help reduce the risk of complications, according to research.

Allergic rhinitis: Most cases of allergic rhinitis are generally mild, and do not cause complications during pregnancy. Common symptoms include cough, headache, itchy nose, itchy mouth, itchy throat, itchy skin, nosebleeds, impaired smell, watery eyes, sore throat, wheezing, fever, cross-reactivity allergy to some fruits, conjunctivitis (pinkeye), nasal congestion, post-nasal drip, runny nose, and swelling of the nasal tissues.

Non-allergic rhinitis (rhinitis of pregnancy): Symptoms of non-allergic rhinitis are the same as allergic rhinitis.

Allergic asthma: Common symptoms include: bronchospasms (abnormal contraction of the bronchi resulting in airway obstruction), coughing (constantly or intermittently), wheezing or whistling sounds when exhaling, shortness of breath or rapid breathing, chest tightness or chest pain, and fatigue. Infants may have trouble feeding and may grunt during suckling.

Skin testing: While skin testing is the most common method of allergy testing, it is generally not performed in pregnant women because there is a slight risk of anaphylaxis, a severe allergic reaction. Anaphylaxis is a rapid, allergic reaction that affects the whole body. 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.

Radioallergosorbent test (RAST®): A radioallergosorbent test (RAST®) is considered a safe alternative for pregnant women. A RAST® is a type of blood test that can determine whether a patient is allergic to particular substances. During the procedure, a sample of the patient's blood is exposed 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. A qualified healthcare provider will interpret the results of the test. In general, the sensitivity of these tests ranges from 50-90%, with the average being about 70-75%. The patient will receive test results in about seven to 14 days.