Types of allergic disease
The existence of IgE antibodies is common to all forms of allergic disease. But the physical symptoms differ depending on the type of mediator released and where they act. When a person with allergies begins to experience symptoms, key questions are: What allergens am I reacting to? When, and how much, am I exposed to these substances?
Major allergic diseases include :
- allergic rhinitis, or "hay fever;"
- allergic conjunctivitis (an eye reaction);
- asthma;
- atopic dermatitis, or allergic skin reactions;
- urticaria, also known as hives;
- severe allergic reactions to substances such as food, latex, medications, and insect stings;
- and problems commonly resulting from allergic rhinitis—sinusitis and otitis media (ear infections).
Symptoms of allergic rhinitis, commonly referred to as "hay fever," occur when allergens touch the lining of the nose—called the mucus membranes—of a person who is sensitive to that particular allergen. Allergic rhinitis is characterized by congestion, itching and dripping of the nose and itchy, watery eyes. If the person continues to have daily, ongoing exposure to the responsible allergen(s), the symptoms will continue. Similar to allergic rhinitis, allergic conjunctivitis occurs when the eyes react to allergens with symptoms of reddening, itching and swelling.
Symptoms of atopic dermatitis, also called eczema, often result from allergen exposure to the skin. Dermatitis symptoms include itching, reddening, and flaking or peeling of the skin. Symptoms begin in childhood for 80% of those with atopic dermatitis. Dermatitis often precedes other allergic disorders; over 50% of those with atopic dermatitis also develop asthma.
Urticaria, or hives, another allergic skin reaction, is characterized by itchy red bumps that can occur in clumps and be either large or small. Hives are often triggered by infection, certain foods or medications. Foods commonly associated with hives include nuts, tomatoes, shellfish and berries. Medications include penicillin, sulfa, anti-seizure medications, phenobarbital and aspirin.
Asthma is a chronic lung disease that affects more than 17 million Americans and is characterized by coughing, chest tightness, shortness of breath and wheezing. Allergic rhinitis is considered a risk factor in developing asthma: up to 78% of those with asthma also have allergic rhinitis.
When an individual experiences asthma symptoms, the inflamed airways become constricted so it becomes more difficult to breathe through the narrowed air passages. For those with allergies, inhaling allergens may produce increased inflammation of the airway lining and further narrowing of the air passages. Asthma may also occur as a result of other stimuli, such as respiratory tract infections or exposure to irritants.
Individuals who have allergies to specific foods may have severe and possibly life-threatening reactions if they eat them. The most common food allergy triggers are the proteins in cow’s milk, eggs, peanuts, wheat, soy, fish, shellfish and tree nuts. Food allergy occurs more frequently in children than adults. Many of these children may lose their sensitivity to particular foods over time.
Foods and other allergens, including penicillin, insect stings and latex, can trigger a severe, systemic allergic reaction called anaphylaxis. Anaphylaxis is caused by swelling throughout the body, and can involve several organ systems. Symptoms of anaphylaxis include a feeling of warmth, flushing, tingling in the mouth or a red, itchy rash. Other symptoms may include feelings of light-headedness, shortness of breath, severe sneezing, anxiety, stomach or uterine cramps, and/or vomiting and diarrhea. In severe cases, patients may experience a drop in blood pressure that results in a loss of consciousness and shock. Without immediate treatment with an injection of epinephrine (adrenalin), anaphylaxis may be fatal.
Sinusitis and otitis media are other common allergic diseases that often are triggered by allergic rhinitis. Sinusitis is an acute or chronic inflammation of the nasal sinuses, which are hollow cavities within the cheek bones found around the eyes and behind the nose. This condition affects over 15% of the U.S. population. Otitis media—or ear infections—is the most common childhood disease requiring physician care. If not properly treated, it can affect a child’s speech and language development.
You can learn more about various allergic diseases by reading the appropriate Tips brochures in this series.
