Diagnosis of Allergies
Allergies Diagnosis: Book Excerpts
Tests and diagnosis discussion for Allergies:
Something in the Air Airborne Allergens: NIAID (Excerpt)
If the patient's medical history indicates that the symptoms recur at
the same time each year, the physician will work under the theory that a
seasonal allergen (like pollen) is involved. Properly trained specialists
recognize the patterns of potential allergens common during local seasons and
the association between these patterns and symptoms. The medical history
suggests which allergens are the likely culprits. The doctor also will examine
the mucous membranes, which often appear swollen and pale or bluish in persons
with allergic conditions.
Skin Tests
Doctors use skin tests to determine whether a patient has IgE antibodies in
the skin that react to a specific allergen. The doctor will use diluted extracts
from allergens such as dust mites, pollens, or molds commonly found in the local
area. The extract of each kind of allergen is injected under the patient's skin
or is applied to a tiny scratch or puncture made on the patient's arm or
back.
Skin tests are one way of measuring the level of IgE antibody in a patient.
With a positive reaction, a small, raised, reddened area (called a wheal) with a
surrounding flush (called a flare) will appear at the test site. The size of the
wheal can give the physician an important diagnostic clue, but a positive
reaction does not prove that a particular pollen is the cause of a patient's
symptoms. Although such a reaction indicates that IgE antibody to a specific
allergen is present in the skin, respiratory symptoms do not necessarily
result.
Blood Tests
Although skin testing is the most sensitive and least costly way to identify
allergies in patients, some patients such as those with widespread skin
conditions like eczema should not be tested using that method. There are other
diagnostic tests that use a blood sample from the patient to detect levels of
IgE antibody to a particular allergen. One such blood test is called the RAST
(radioallergosorbent test), which can be performed when eczema is present or if
a patient has taken medications that interfere with skin testing. (Source: excerpt from Something in the Air Airborne Allergens: NIAID)
Allergies: NWHIC (Excerpt)
Often skin tests
or blood tests are used to determine specific antibody levels reacting to
a certain allergen. If there are unusually high levels of an antibody
known as IgE, it is a good indication of an allergic reaction. (Source: excerpt from Allergies: NWHIC)
Diagnosis of Allergies: medical news summaries:
The following medical news items
are relevant to diagnosis and misdiagnosis issues for Allergies:
Diagnostic Tests for Allergies: Online Medical Books
16 MEDICAL BOOKS ONLINE!
Review excerpts from medical books online, free, without registration,
for more information about diagnostis of Allergies.
Urticaria:
Differential Diagnosis
(In a Page: Signs and Symptoms)
-
Idiopathic urticaria without angioedema
–Most common diagnosis in patients with hives
–Often related to food or drug allergies, bites, or stings
–25% of patients with one episode will progress to chronic urticaria
-
Chronic urticaria
–Idiopathic in 50% of cases
–Chronic idiopathic urticaria spontaneously
resolves within 2 years in 80% of patients
–Criterion for chronic urticaria is duration of more than 6 weeks
-
Occult infection (e.g., sinusitis, oral infection, cholecystitis, vaginitis, prostatitis, hepatitis, HIV, tinea manus or pedis)
-
Malignancy
-
Thyroid disease
-
Drugs (e.g., radiocontrast media, penicillin, salicylates, benzoates, azo dyes)
–May result in life-threatening episodes of urticaria and acute angioedema that can lead to anaphylaxis -
Urticaria secondary to physical stimuli [e.g., exercise (cholinergic), vibratory pressure, sun exposure (solar urticaria), cold exposure]
–Dermographism occurs in 5% of the population; manifests as a physical urticaria that arises in the distribution line of a scratch or rubbed skin area -
Hereditary or acquired deficiency of complement factor C1
–Generally appears as episodic angioedema in the absence of urticaria
–Only in the absence of urticaria should hereditary or acquired complement deficiency be considered
-
Angioedema-urticaria-eosinophilia syndrome
–Associated with elevated serum IgE, fever, and fluid retention during an acute attack -
Urticarial vasculitis
–Presents as urticaria that lasts longer than 12–24 hours
–Associated with autoimmune disease (e.g., systemic lupus erythematosus)
-
Cutaneous mastocytosis/urticaria pigmentosa
Workup and Diagnosis
- Complete history and physical examination
–Family history of angioedema, anaphylaxis, etc.
–Seasonal or activity-related (work/home) symptoms
–Note whether urticaria occurs after ingestion of certain
foods or with physical stimuli (e.g., exercise, pressure)
–Physical exam should evaluate for underlying occult infections (e.g., UTI, vaginal yeast infection, tinea)
–Firmly trace the blunt tip of a cotton applicator across the patient's back; patients with dermographism will develop a pruritic urticarial wheal within 5 minutes
-
Determine whether the patient has isolated urticaria, urticaria with angioedema, or isolated angioedema
-
Consider sinus X-rays, T4, TSH, and thyroid antibodies
-
In isolated angioedema without urticaria, check C2, C4, and/or C1 esterase inhibitor serum levels
-
IgE level measurement is indicated if angioedema-urticariaeosinophilia syndrome is suspected
-
If urticarial lesions last longer than 12–24 hours, a punch biopsy of the involved skin is indicated to confirm the presence of vasculitis
-
Perform age-appropriate malignancy screening
-
If a cause cannot be found, consider referral to a dermatologist to rule out an occult etiology, although many cases will ultimately be deemed idiopathic
» READ BOOK EXCERPT ONLINE »
Source: In a Page: Signs and Symptoms, 2004
Urticaria:
Differential Diagnosis
(In A Page: Pediatric Signs and Symptoms)
- Urticaria
–Epidemiology: Lifetime incidence 20%; most cases resolve within 48 hours; chronic
>6 weeks
–Pathophysiology: Hypersensitivity reaction: allergens (IgE-mediated, prior sensitization), complement, and other cytokines activate mast cells and basophils to release histamine (also kinins, prostaglandins, serotonin) with plasma extravasation; wheals/hives: dermis edema
–Triggers: Most cases are idiopathic
–IgE-mediated: Insects (bees, wasps, scorpions, spiders, jellyfish), foods (eggs, shellfish, tree nuts, peanuts, tomatoes), drugs (penicillins, cephalosporins, NSAIDs, barbiturates, amphetamines, insulin, blood products), pollen, danders, food additives
–Non-IgE-mediated: Infections (strep, EBV; hepatitis A, B, and C; adenovirus, enterovirus; fleas, mites), drugs (opiates, acetylsalicylic acid, local anesthetics), physical (exercise, cold/heat, UV light, water, pressure), contrast dyes, latex
-
Chronic urticaria: Associated with collagen vascular diseases (SLE, cryoglobulinemia), inflammatory bowel disease, malignancy, thyroiditis, hyperthyroidism, Behçet disease, vasculitis
-
Angioedema: 50% of urticaria cases; subcutaneous and mucous membrane edema
-
Anaphylaxis (IgE-mediated)
–Most potent foods: Peanuts, fish
–Mortality: 100–500 deaths/year in U.S.
–Associated shock has a poor prognosis
-
Hereditary angioedema
–High mortality
–Most cases are autosomal dominant
–C1 esterase inhibitor deficiency
–Recurrent episodes of edema (face, upper
airway, extremities)
–Triggers: Trauma, surgery
–Unresponsive to epinephrine, antihistamines
-
Others: Erythema multiforme, mastocytosis, guttate psoriasis, flushing, cellulitis
Workup and Diagnosis
- History: Exposure to triggers, associated symptoms, symptoms of hypo-/hyperthyroidism, “feeling of impending doom” (anaphylaxis), history of atopy, family history of systemic diseases
- Physical exam
–Wheals/hives: Transient, elevated, erythematous, severely pruritic plaques, sudden onset; each wheal lasts 30 minutes to 3 hours, reappearing in other areas
–Papular uritcaria: 2–3 mm red papules surrounded by 10–20 mm wheals, most common in toddlers, due to fleas and mites (e.g., scabies)
–Physical urticaria: 10–20 mm erythematous macules with central wheal
–Angioedema: Edema of face, hands, feet, genitalia
–Anaphylaxis: Irritability, wheals, broncho- or laryngospasm (wheezing/stridor), angioedema, hypotension (late finding in children), vomiting, bloody diarrhea, mental status change; develops over minutes to hours; may develop DIC
–Hereditary angioedema: Nonpruritic edema
- Labs/studies
–Urticaria/anaphylaxis: IgE antibody skin test or radioallergosorbent test for IgE-mediated causes; culture, microscopy (ova and parasites)
–Angioedema: C1 esterase inhibitor, C3, C4
–Chronic urticaria: ANA, urinalysis, CBC, CRP, ESR, thyroid antibodies
» READ BOOK EXCERPT ONLINE »
Source: In A Page: Pediatric Signs and Symptoms, 2007
Urticaria [Hives]:
History
(Handbook of Signs & Symptoms (Third Edition))
If the patient isn’t in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is there a relationship to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has the patient recently changed or used new skin products or detergents? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Signs & Symptoms (Third Edition), 2006
Allergic purpuras:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
No laboratory test clearly identifies allergic purpura (although white blood cell count and erythrocyte sedimentation rate are elevated). Diagnosis therefore necessitates careful clinical observation, in many cases during the second or third attack. Except for a positive tourniquet test (a test to assess the capillaries’ability to withstand increased pressure), coagulation and platelet function tests are usually normal. Small-bowel X-rays may reveal areas of transient edema; in many cases, tests for blood in the urine and stool are positive. Increased blood urea nitrogen and creatinine levels may indicate renal involvement. Diagnosis must rule out other forms of nonthrombocytopenic purpura.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Allergic rhinitis:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
Microscopic examination of sputum and nasal secretions reveals large numbers of eosinophils. Blood chemistry shows normal or elevated IgE. A definitive diagnosis is based on the patient’s personal and family history of allergies as well as physical findings during a symptomatic phase. Skin testing paired with tested responses to environmental stimuli can pinpoint the responsible allergens given the patient’s history. In patients who can’t tolerate skin testing, the radioallergosorbent test may be helpful in determining specific allergen sensitivity.
To distinguish between allergic rhinitis and other nasal mucosa disorders, remember these differences:
❑ In chronic vasomotor rhinitis, eye symptoms are absent, rhinorrhea is mucoid, and seasonal variation is absent.
❑ In infectious rhinitis (the common cold), the nasal mucosa is beet red; nasal secretions contain polymorphonuclear, not eosinophilic, exudate; and signs and symptoms include fever and sore throat. This condition isn’t a recurrent seasonal phenomenon.
❑ In rhinitis medicamentosa, which results from excessive use of nasal sprays or drops, nasal drainage and mucosal redness and swelling disappear when such medication is withheld.
❑ In children, differential diagnosis should rule out a nasal foreign body, such as a bean or a button.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Latex allergy:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
A patient who describes even the mildest symptoms during a history and physical assessment should be suspected of having a latex allergy. The patient may describe dermatitis or mild respiratory distress when using latex gloves, inflating a balloon, or coming in contact with other latex products.
Confirming diagnosis A blood test for latex sensitivity can confirm the diagnosis. This test, which measures specific immunoglobulin E antibodies against latex, should be used only when latex allergy is suspected; it isn’t recommended as a screening tool.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Urticaria and angioedema:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
An accurate patient history can help determine the cause of urticaria. Such a history should include:
❑ drug history, including over-the-counter preparations (vitamins, aspirin, and antacids)
❑ frequently ingested foods (strawberries, milk products, fish)
❑ environmental influences (pets, carpet, clothing, soap, inhalants, cosmetics, hair dye, and insect bites and stings).
Diagnosis also requires physical assessment to rule out similar conditions as well as a complete blood count, urinalysis, erythrocyte sedimentation rate, and a chest X-ray to rule out inflammatory infections. Skin testing, an elimination diet, and a food diary (recording time and amount of food eaten and circumstances) can pinpoint provoking allergens. The food diary may also suggest other allergies. For instance, a patient allergic to fish may also be allergic to iodine contrast materials.
Recurrent angioedema without urticaria, along with a familial history, points to hereditary angioedema. (See Hereditary angioedema.) Decreased serum levels of complement 4 and complement 1 esterase inhibitors confirm this diagnosis.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Urticaria [Hives]:
History
(Professional Guide to Signs & Symptoms (Fifth Edition))
If the patient isn’t in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is it related to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has he recently used new skin products? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Signs & Symptoms (Fifth Edition), 2006
Urticaria:
History
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
A. Characteristics. Is the rash localized or systemic? Is it pruritic? What is the duration of symptoms? Does anything relieve the symptoms? Are there any specific triggers (2)?
1. Food and drugs are common causes of urticaria.
2. Certain systemic diseases can cause urticaria. Infections, connective tissue disorders, endocrine disorders, and neoplastic disorders are some examples.
3. Insect stings and bites are another common cause of urticaria.
B. Symptom chronology. When does it occur? How long does it last? Is it in association with physical trauma? Has the patient been on any medication that has helped relieve symptoms (e.g., antihistamines)?
C. Family history. Are there any members of the family who suffer from a connective tissue disorder? Do any complement disorders occur in the family, such as hereditary angioedema, which can be associated with urticaria? Also, is there a family history of atopy?
Physical examination
A complete physical is required to rule out infection or other systemic diseases. An urticarial wheal is usually well demarcated. It begins as an erythematous area, which then develops a white center. The size of the wheal can vary from 2 mm to well over 30 cm. The rash is usually pruritic, especially when it occurs on the palms of the hand and the soles of the feet. Most often, the wheal will disappear within 3 to 4 hours of onset. The accompanying angioedema can last for a couple of days. The skin will return to normal once the wheal is gone.
» READ BOOK EXCERPT ONLINE »
Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Urticaria/Angioedema:
Differential Overview
(Field Guide to Bedside Diagnosis)
❑ Ingestants
❑ Drugs
❑ Inhalants
❑ Hymenoptera venom
❑ Latex sensitivity
❑ Dermatographism
❑ Pressure urticaria
❑ Cholinergic urticaria
❑ Cold urticaria
❑ Solar urticaria
❑ Infection
❑ Urticarial vasculitis
❑ Hereditary angioedema
❑ Mastocytosis
Diagnostic Approach
Urticaria appears as transient, mutable wheals with red raised serpiginous borders and clear centers, which often coalesce. Urticaria is experienced by 10% to 20% of the population at some time. Angioedema is well-demarcated localized edema.
The appearance may be helpful. Gyrate hives (erythema gyratum) are associated with internal malignancy. Hives without pseudopods suggest allergy. Small lesions with erythematous flares suggest cholinergic urticaria. Urticarial lesions unchanged for 24 hours suggest vasculitis, especially if associated with scaling or purpura.
» READ BOOK EXCERPT ONLINE »
Source: Field Guide to Bedside Diagnosis, 2007
anaphylaxis:
Diagnosis
(Handbook of Diseases)
Anaphylaxis can be diagnosed by the rapid onset of severe respiratory or cardiovascular symptoms after ingestion or injection of a drug, vaccine, diagnostic agent, food, or food additive or after an insect sting. If these symptoms occur without a known allergic stimulus, rule out other possible causes of shock (such as acute myocardial infarction, status asthmaticus, and heart failure).
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Allergic purpura:
Diagnosis
(Handbook of Diseases)
No laboratory test result clearly identifies allergic purpura (although the white blood cell count and erythrocyte sedimentation rate are elevated). Diagnosis therefore requires careful observation, usually during the second or third attack. Except for a positive tourniquet test result, coagulation and platelet function test results are usually negative. X-rays of the small bowel may reveal areas of transient edema; test results for blood in the urine and stool are often positive. Increased blood urea nitrogen and serum creatinine levels may indicate renal involvement. The diagnosis must rule out other forms of nonthrombocytopenic purpura.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Allergic rhinitis:
Diagnosis
(Handbook of Diseases)
Microscopic examination of sputum and nasal secretions reveals large numbers of eosinophils. Blood chemistry studies show normal or elevated IgE levels, possibly linked to seasonal overproduction of interleukin-4 and -5 (involved in the allergic inflammatory process). A firm diagnosis rests on the patient’s personal and family history of allergies and on physical findings during a symptomatic phase. Skin testing, paired with tested responses to environmental stimuli, can help pinpoint the responsible allergens when interpreted in light of the patient’s history.
To distinguish between allergic rhinitis and other disorders of the nasal mucosa, remember these differences:
With chronic vasomotor rhinitis, eye symptoms are absent, rhinorrhea is mucoid, and seasonal variation is absent.
CLINICAL TIP: With infectious rhinitis (the common cold), the nasal mucosa is red; nasal secretions contain polymorphonuclear, not eosinophilic, exudate; and signs and symptoms include fever and sore throat. This condition isn’t a recurrent seasonal phenomenon.
With rhinitis medicamentosa, which results from excessive use of nasal sprays or drops, nasal drainage and mucosal redness and swelling disappear when such medication is withheld.
In children, a differential diagnosis should rule out the presence of a foreign body in the nasal passage, such as a bean or a button.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Urticaria and angioedema:
Diagnosis
(Handbook of Diseases)
An accurate patient history can help determine the cause of urticaria. Such a history should include:
❑ drug history, including over-the-counter preparations (vitamins, aspirin, and antacids)
❑ frequently ingested foods (strawberries, milk products, fish)
❑ environmental influences (pets, carpet, clothing, soap, inhalants, cosmetics, hair dye, and insect bites and stings).
Diagnosis also requires physical assessment to rule out similar conditions, as well as a complete blood count, urinalysis, erythrocyte sedimentation rate, and a chest X-ray to rule out inflammatory infections. Skin testing, an elimination diet, and a food diary (recording time and amount of food eaten and circumstances) can pinpoint provoking allergens. The food diary may also suggest other allergies. For instance, a patient allergic to fish may also be allergic to iodine contrast materials.
Recurrent angioedema without urticaria, along with a familial history, points to hereditary angioedema. Decreased serum levels of complement 4 and complement 1 esterase inhibitors confirm this diagnosis.
» READ BOOK EXCERPT ONLINE »
Source: Handbook of Diseases, 2003
Urticaria:
History
(Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series)
If the patient isn’t in distress, obtain his medical history. Does he have known allergies? Does urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is there a relationship to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has the patient recently changed or used new skin products? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note a history of chronic or parasitic infection, skin disease, or GI disorder.
Physical examination
Obtain the patient’s vital signs. Perform a complete cardiopulmonary assessment, noting signs and symptoms of shock or respiratory distress. Assess for urticaria in other areas because new crops may continue to appear.
» READ BOOK EXCERPT ONLINE »
Source: Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series, 2007
Urticaria:
History
(Signs & Symptoms: A 2-in-1 Reference for Nurses)
If the patient isn’t in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is there a relationship to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has the patient recently changed or used new skin products? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
» READ BOOK EXCERPT ONLINE »
Source: Signs & Symptoms: A 2-in-1 Reference for Nurses, 2007
Urticaria [Hives]:
History and physical examination
(Nursing: Interpreting Signs and Symptoms)
If the patient isn't in distress, obtain a complete history. Does he have any known allergies? Does the urticaria follow a seasonal pattern? Do certain foods or drugs seem to aggravate it? Is there a relationship to physical exertion? Is the patient routinely exposed to chemicals on the job or at home? Has the patient recently changed or used new skin products or detergents? Obtain a detailed drug history, including prescription and over-the-counter drugs. Note any history of chronic or parasitic infection, skin disease, or a GI disorder.
Next, assess respiratory status. Inspect the chest for sternal retractions and accessory muscle use. Auscultate and percuss the chest. Assess cardiac status. Obtain vital signs and pulse oximetry and begin cardiac monitoring. Assess all skin surfaces.
» READ BOOK EXCERPT ONLINE »
Source: Nursing: Interpreting Signs and Symptoms, 2007
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