An allergy is an exaggerated immune response or reaction to substances that are generally not harmful. Causes
Allergies are relatively common. Both genetics and environmental factors play a role.
The immune system normally protects the body against harmful substances, such as bacteria and viruses. It also reacts to foreign substances called allergens, which are generally harmless and in most people do not cause a problem.
But in a person with allergies, the immune response is oversensitive. When it recognizes an allergen, it releases chemicals such as histamines. which fight off the allergen. This causes itching, swelling, mucus production, muscle spasms, hives, rashes, and other symptoms of allergies, which vary from person to person.Common allergens include pollen, mold, pet dander, and dust. Food and drug allergies are common. Allergic reactions can also be caused by insect bites, jewelry, cosmetics, spices, and other substances.
Some people have allergy-like reactions to hot or cold temperatures, sunlight, or other environmental triggers. Sometimes, friction (rubbing or roughly stroking the skin) will cause symptoms.
A specific allergy is not usually passed down through families (inherited). However, if both your parents have allergies, you are likely to have allergies. The chance is greater if your mother has allergies.
Allergies may make certain medical conditions such as sinus problems, eczema, and asthma worse.
Symptoms
Allergy symptoms vary, but may include:
Breathing problems (coughing, shortness of breath)
Burning, tearing, or itchy eyes
Conjunctivitis (red, swollen eyes)
Coughing
Diarrhea
Headache
Hives
Itching of the nose, mouth, throat, skin, or any other area
Runny nose
Skin rashes
Stomach cramps
Vomiting
Wheezing
What part of the body is contacted by the allergen plays a role in the symptoms you develop. For example:
Allergens that are breathed in often cause a stuffy nose, itchy nose and throat, mucus production, cough, or wheezing
Allergens that touch the eyes may cause itchy, watery, red, swollen eyes.
Eating something you are allergic to can cause nausea, vomiting, abdominal pain, cramping, diarrhea, or a severe, life-threatening reaction
Allergens that touch the skin can cause a skin rash, hives, itching, blisters, or even skin peeling
Drug allergies usually involve the whole body and can lead to a variety of symptoms
Treatment
Severe allergic reactions (anaphylaxis) require treatment with a medicine called epinephrine, which can be life saving when immediately given.
The best way to reduce symptoms is to try and avoid what causes your allergies in the first place. This is especially important for food and drug allergies.
There are several types of medications available to prevent and treat allergies. Which medicine your doctor recommends depends on the type and severity of your symptoms, your age, and overall health.
Specific illnesses that are caused by allergies (such as asthma, hay fever, and eczema) may require other treatments.
Medications that can be used to treat allergies include:
ANTIHISTAMINES
Antihistamines are available over-the-counter and by prescription. They are available in many forms, including:
Capsules and pills
Eye drops
Injection
Liquid
Nasal spray
Click here to see a video about how to use nasal sprays.
CORTICOSTEROIDS
Anti-inflammatory medications (corticosteroids) are available in many forms, including:
Creams and ointment for the skin
Eye drops
Nasal spray
Lung inhaler
Patients with severe allergic symptoms may be prescribed corticosteroid pills or injections for short periods of time.
DECONGESTANTS
Decongestants can help relieve a stuffy nose. Decongestant nasal spray should not be used for more than several days, because they can cause a "rebound" effect and make the congestion worse. Decongestants in pill form do not cause this problem.
OTHER MEDICINES
Leukotriene inhibitors are medicines that specifically block the substances that trigger allergies. Zafirlukast (Accolate) and montelukast (Singulair) are approved for those with asthma and indoor and outdoor allergies.
ALLERGY SHOTS
Allergy shots (immunotherapy) are occasionally recommended if the allergen cannot be avoided and symptoms are hard to control. Allergy shots keep your body from over-reacting to the allergen. Regular injections of the allergen are given, with each dose slightly larger than the previous dose until a maximum dose is reached. They do not work for everybody and require frequent doctor's visits.