An allergy is an exaggerated immune response or reaction to substances that are generally not harmful.
- Allergic conjunctivitis
- Allergic reactions
- Allergy testing
- Allergy to mold, dander, dust
- Atopic dermatitis (eczema)
- Contact dermatitis
- Drug allergies
- Food allergies
- Hay fever (allergic rhinitis)
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, 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.
Allergy symptoms vary, but may include:
- Breathing problems
- Burning, tearing, or itchy eyes
- Conjunctivitis (red, swollen eyes)
- Itching of the nose, mouth, throat, skin, or any other area
- Runny nose
- Skin rashes
- Stomach cramps
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
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 are available over-the-counter and by prescription. They are available in many forms, including:
- Capsules and pills
- Eye drops
- Nasal spray
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 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.
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 (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.
Most allergies can be easily treated with medication.
Some children may outgrow an allergy. This is particularly true of food allergies. However, as a general rule, once a substance has triggered an allergic reaction, it continues to affect the person.
Allergy shots are most effective when used to treat those with hay fever symptoms and severe insect sting allergies. They are not used to treat food allergies because of the danger of a severe reaction. Allergy shots may require years of treatment, but they work in most cases. However, they may cause uncomfortable side effects (such as hives and rash) and dangerous outcomes (such as anaphylaxis).
Breast-feeding children for at least 4 months or more may help prevent atopic dermatitis cow milk allergy, and wheezing in early childhood.
However, changing a mother's diet during pregnancy or while breast-feeding does not seem to help prevent allergy-related conditions.
For most children, changing diet or special formulas does not seem to prevent these problems. If there is a family history of eczema and allergies in a parent, brother, or sister, discuss the infant feeding with your child's doctor. The timing of introduction of solid foods in general, as well as use of several specific foods, can help prevent some allergies.
There is also evidence that infants exposed to certain airborne allergens (such as dust mites and cat dander) may be less likely to develop related allergies. This is called the "hygiene hypothesis" and sprang from observations that infants on farms tend to have fewer allergies than those who grow up in environments that are more sterile.
Once allergies have developed, treating the allergies and carefully avoiding those things that cause reactions can prevent allergies in the future.